I certainly can't argue that Princess Talanji fits into any good decks right now, but I think you're being a little unfair to Blizzard with respect to the support. We've seen Control Priest decks with a lot of Thief Priest tools in the past (e.g. Drakonid Operative, Entomb, and Archbishop Benedictus). Those decks tend to shine most when their tools gain them tempo and steal cards (all of the wild cards I mentioned, and in Standard something like [Hearthstone Card (Madam Lazul) Not Found] or maybe Holy Water despite its horrible cost).
There's no shortage of tools that support thieving in Priest: Thoughtsteal, Mind Vision, Seance, and Cloning Device are all tools in Standard on top of the ones I mentioned above, and there are even more in Wild. The problem with them is that they're all zero tempo, high value plays. They can work in a slow meta game, but have limited applications outside of that. And all that seems quite appropriate - if Priest got lots and lots of high tempo thief cards, they'd probably be very unbalanced (see Drakonid Operative as a prime example of this).
Khartut Defender seems like a strong anti-aggro tool - heal for 6, absorb at least 4 damage with your taunts, and deal 3 to two creatures does a lot of work. However, coming down one turn 6 might mean you're just dead anyway - we saw that back in the days of Reno Jackson, where even getting a super massive heal may not save you against high pressure aggro. Hopefully the taunts will take one or two minions with them and shift the tempo enough to make this impactful.
Wretched Reclaimer, on the other hand, is a ridiculously powerful card. It's just barely understated, and can target any deathrattle and/or reborn minion to huge effect. This is going to be particularly interesting in conjunction with Embalming Ritual. Compared to Reincarnate in Shaman, it's a 1 mana 3/3 attached to a 2 mana spell in a class that cares a lot more about a) minions being at full health for OTKs, etc., and b) deathrattles triggering multiple times.
Sahket Sapper is an interesting anti-aggro tool - trades with one or two minions and then bounces another - and the fact that it's a deathrattle fits reasonably well with Anka, the Buried (maybe with a Mecha'thun win condition). Deathrattle Rogue has a lot of interesting pieces, but as always it's never clear that this deck has enough gas, or more power than a standard tempo/combo Rogue.
King Phaoris is gonna be a lot of fun in a big spell mage and Res Priest. You really only need one or two big spells in hand to make this well worth the cost.
On its own, Conjured Mirage is a decent tool against aggro. Followed up immediately by Doomsayer on turn 6, it's a solid 6 mana board clear most of the time for any deck trying to play control. Control Paladin was fine running a two-card 6 mana combo with pre-nerf Equality + Consecration, so this seems like a very viable neutral board clear combo for any class that needs it.
I don't think this is quite a reprint of Desperate Stand - in fact, I think it's strictly weaker (but not worse, as the one mana discount is huge). A creature can stack multiple deathrattle effects, even if those effects are equivalent, but I don't think a creature can benefit from the same keyword more than once (e.g. giving a windfury minion windfury doesn't give it mega-windfury, etc.). So, presumably, you get no benefit from casting this on a reborn monster, and no benefit from stacking it with itself. That's not a huge difference, but I think it explains the one-mana difference.
Tomb Warden is pretty fair for its cost even before you do any buffing, so this seems great if you can get some buffs on it. And it comes down way later than Saronite Chain Gang, so it should be way less busted.
Dark Pharaoh Tekahn is a great card - the power of Crystal Core attached to a 4/4 body is pretty compelling, and the fact that it will only affect up to 6 cards (at least today - 2x EVIL Genius and 2x EVIL Cable Rat) means its power level is not absurdly oppressive. This may limit the extent to which Warlock can get more lackey generating tools - we don't need a new Quest Rogue deck in the meta - but it may also make for some wacky games where you fill your hand with lackeys and use Plot Twist + Augmented Elekk with Fel Lord Betrug and/or Dollmaster Dorian to get a bunch of extra 4/4s both in play and in hand. Given the sheer power of each lackey's battlecry, shuffling a bunch into your deck actually doesn't seem like a crazy thing to do.
Sort of a bummer that EVIL Recruiter ends up far less impactful after you've dropped Dark Pharaoh Tekahn, but it's still a great effect if you use your 4/4 lackey to value trade and then destroy it to get a 5/5 with (potentially) relevant tribal synergies.
This is not a perfect comparison, but looking at Desert Spear reminds me of the discussions around Ray of Frost. A lot of people felt that it was strictly outclassed by other options like Frostbolt, but the flexibility of directing its effect at multiple targets, and other synergies for cheap spells, make it a very useful card that sees a lot of play.
It can be a 3 mana 2/3 weapon, which is fair for the cost
It can be a way to deal 1 damage to two separate targets (which is particularly relevant against reborn creatures and/or in conjunction with Hunter's Mark, but also good as a way to manage an enemy aggro deck and hold early game tempo)
It can generate a decent, on-curve target for Dire Frenzy or an easy way to activate Wing Blast
It's not a terribly flashy card, but it does enough that it shouldn't be underestimated.
Magma Rager is obviously not a great example, but as others have said this is a good tool for cleaning up Reborn creatures without spending extra resources.
[cardPlague of Flames is a nice card and it's clearly got a lot of Warlock flavor, but I'm not convinced it's all that good.
In combination with Rafaam's Scheme or Fiendish Circle it's frequently a 4 or 5 mana board clear. In most classes, a two-card board clear for 4 or 5 mana would compare pretty favorably to pre-nerf Equality + Consecration and you'd probably see it played, but Warlock has lots of good board clears already.
On top of the fact that Warlock already has lots of good single-card board clears, this combo relies on bad imp generating cards, and Rafaam's Scheme needs to be in your hand for a while before the combo can even be triggered. There are already a lot of potential synergies for these imp generating cards in the form of Jumbo Imp, Darkest Hour, and Demonbolt. None of that came together last expansion, and I'm not sure one extra board clear is going to make them good. Maybe you'll see a few games where this combo clears the board and enables you to play a cheap 8/8 Jumbo Imp, but banking on that seems like a bad idea.
The typical baseline for drawing 4 cards in 7 mana (i.e. Sprint), so the fact that Overflow draws one more card for the same mana is already ridiculous. Throw in the healing and synergy with Anubisath Defender and you've got a ridiculously powerful card.
Easily Reno the Relicologist - the "gattling wand" concept and art is super fun, and I love highlander decks and have missed them since Mean Streets of Gadgetzan rotated.
So, this is basically a Master Swordsmith that can't be killed in one hit, synergies with Making Mummies, and slots decently well into Mech Paladin. Seems pretty great, and will easily find at least one archetype to be good in.
Lots of value - spend 2 mana, get 1/2 + a 1/1 and a +1/+1 on death, then another +1/+1 on second death gets you to 4/5 in stats for 2 over time. As long as you can build a decently wide board, this is pretty good, but there have been lots of efforts to make this work and they've largely failed in Priest.
Hard to imagine a deck that wants Generous Mummy. It's a lot of early tempo, but so is Marsh Drake and its drawback is much easier to deal with for classes that want to capitalize on early tempo. The reborn effect might be a boon to keep the tempo going, but making your opponents cards cost 1 less means enemy AoE is coming in earlier to clean up your board. Where this might be useful is as a tech card for aggro mirrors, where you expect your opponent will play out their hand early and get very little benefit from this, or maybe in some Paladin aggro deck that wants to use Rebuke to mitigate the benefit to your opponent long enough to get a win.
I seem to recall Blizzard saying that they don't like the Inner Fire + Divine Spirit combos because it's not compatible with the class identity, but High Priest Amet obviously makes that very easy with Stonetusk Boar. This may be a harbinger for a hall of fame rotation for one or both of those combo pieces - Blizzard has said that they think it's fine to produce super powerful combos as long as they rotate after a few months (this was in a reflection on the failure of the Highlander/Anduin's tenure in standard), so they may be getting ready to give that combo one last hurrah before "hall of faming" it.
Outside of combos, because High Priest Amet's text reads "summon" rather than "play," he does a lot of cool stuff with reborn effects, etc., and after the almost certain hall of fame rotation of OTK Priest, I expect we'll see him used for some pretty serious value plays.
Mogu Cultist is driving me nuts! It seems so ridiculously hard to pull off. I'm not sure I've found any truly good way to do it, but here are some ideas on how to achieve this. The standard shuffle/draw/bounce package each class has access to is Augmented Elekk + Baleful Banker. With 10 mana, the best you can do is shuffle 4 extra copies (Augmented Elekk + Mogu Cultist + 2x Baleful Banker for 8 mana). Tack on a Youthful Brewmaster and you can start to do this in every class. Here's that, and some other ideas:
Rogue: As everyone has said, is the easiest with Tak Nozwhisker and various shuffle and/or bounce effects. Rogue has so many ways to create and draw enough Cultists that the details barely matter.
Warlock: Aside from the clunky base combo, you have a series of shuffles with Plot Twists with Augmented Elekk and a hand full of Mogu Cultists and Elekks could do it slowly. Another idea is Supreme Archaeology; use it to get a free Glinda Crowskin (hopefully, after some plot twisting, dumb luck, etc.), then echo out your Cultists, kill Glinda with something like Demonbolt and play the last Cultist once she's dead.
Shaman: Complete Corrupt the Waters, then Hero Power + Augmented Elekk+ Mogu Cultist + 2x Baleful Banker puts eight copies of the Cultist in your deck. Use something like Spirit of the Frog or Gadgetzan Auctioneer to help you draw your deck, because getting all those Cultists into your hand will be hard. This doesn't seem entirely crazy to me - Battlecry Control Shaman can already get a lot of value out of a shuffle package, and you only need one cultist to make this work, so it's sort of a tech card for games where you need a more explosive win condition against a very slow opponent.
Mage: The best I've got here on top of that base combo is some kind of deck that draws the whole deck, uses some combination of Augmented Elekks + Mogu Cultists + Baleful Bankers to put three or more copies into the deck, and then drops Archmage Arugal and draws the Cultists.
Druid: Do the base Elekk + Banker combo to get some extra copies (three is fine), then draw your deck and use Elise the Enlightened to get to the critical mass of Cultists. The trickiest part here is killing of Elise - with Naturalize hall of famed, Druid has a hard time killing its own stuff. Maybe Starfall would work - that has the added benefit of fitting nicely into a Quest Druid with this as its win condition.
Paladin: Pretty easy given that base combo mentioned above. Complete Making Mummies, then Augmented Elekk + Mogu Cultist + 2x Baleful Banker + Youthful Brewmaster on the Cultist to get six. Draw them all (somehow...), then play a few, Hero Power, and play the rest to get an active Cultist battlecry in play for 9 mana.
Warrior: This might be the only class that has no current way in standard to beat that base combo (even marginally). Warrior has no extra ways to shuffle Cultists, and no cheap tools to get extra copies into play.
Diseased Vulture seems really strong - turns every tap into "draw a card, summon a 3 drop" for 2. It's high enough health to hand around after the turn you play it, and has natural synergy with useful Zoo cards like Flame Imp, and to a lesser extent with Demonbolt and Riftcleaver.
I certainly can't argue that Princess Talanji fits into any good decks right now, but I think you're being a little unfair to Blizzard with respect to the support. We've seen Control Priest decks with a lot of Thief Priest tools in the past (e.g. Drakonid Operative, Entomb, and Archbishop Benedictus). Those decks tend to shine most when their tools gain them tempo and steal cards (all of the wild cards I mentioned, and in Standard something like [Hearthstone Card (Madam Lazul) Not Found] or maybe Holy Water despite its horrible cost).
There's no shortage of tools that support thieving in Priest: Thoughtsteal, Mind Vision, Seance, and Cloning Device are all tools in Standard on top of the ones I mentioned above, and there are even more in Wild. The problem with them is that they're all zero tempo, high value plays. They can work in a slow meta game, but have limited applications outside of that. And all that seems quite appropriate - if Priest got lots and lots of high tempo thief cards, they'd probably be very unbalanced (see Drakonid Operative as a prime example of this).
Khartut Defender seems like a strong anti-aggro tool - heal for 6, absorb at least 4 damage with your taunts, and deal 3 to two creatures does a lot of work. However, coming down one turn 6 might mean you're just dead anyway - we saw that back in the days of Reno Jackson, where even getting a super massive heal may not save you against high pressure aggro. Hopefully the taunts will take one or two minions with them and shift the tempo enough to make this impactful.
Wretched Reclaimer, on the other hand, is a ridiculously powerful card. It's just barely understated, and can target any deathrattle and/or reborn minion to huge effect. This is going to be particularly interesting in conjunction with Embalming Ritual. Compared to Reincarnate in Shaman, it's a 1 mana 3/3 attached to a 2 mana spell in a class that cares a lot more about a) minions being at full health for OTKs, etc., and b) deathrattles triggering multiple times.
Sahket Sapper is an interesting anti-aggro tool - trades with one or two minions and then bounces another - and the fact that it's a deathrattle fits reasonably well with Anka, the Buried (maybe with a Mecha'thun win condition). Deathrattle Rogue has a lot of interesting pieces, but as always it's never clear that this deck has enough gas, or more power than a standard tempo/combo Rogue.
King Phaoris is gonna be a lot of fun in a big spell mage and Res Priest. You really only need one or two big spells in hand to make this well worth the cost.
On its own, Conjured Mirage is a decent tool against aggro. Followed up immediately by Doomsayer on turn 6, it's a solid 6 mana board clear most of the time for any deck trying to play control. Control Paladin was fine running a two-card 6 mana combo with pre-nerf Equality + Consecration, so this seems like a very viable neutral board clear combo for any class that needs it.
I don't think this is quite a reprint of Desperate Stand - in fact, I think it's strictly weaker (but not worse, as the one mana discount is huge). A creature can stack multiple deathrattle effects, even if those effects are equivalent, but I don't think a creature can benefit from the same keyword more than once (e.g. giving a windfury minion windfury doesn't give it mega-windfury, etc.). So, presumably, you get no benefit from casting this on a reborn monster, and no benefit from stacking it with itself. That's not a huge difference, but I think it explains the one-mana difference.
I love that the art of Embalming Ritual is a resurrection of a cat - really underplays how good this card can be. It has more than enough good targets in standard (Cairne Bloodhoof, Zerek, Master Cloner, Convincing Infiltrator, Mechanical Whelp, etc.), and I expect will be a linchpin in any deck that uses it.
Tomb Warden is pretty fair for its cost even before you do any buffing, so this seems great if you can get some buffs on it. And it comes down way later than Saronite Chain Gang, so it should be way less busted.
Dark Pharaoh Tekahn is a great card - the power of Crystal Core attached to a 4/4 body is pretty compelling, and the fact that it will only affect up to 6 cards (at least today - 2x EVIL Genius and 2x EVIL Cable Rat) means its power level is not absurdly oppressive. This may limit the extent to which Warlock can get more lackey generating tools - we don't need a new Quest Rogue deck in the meta - but it may also make for some wacky games where you fill your hand with lackeys and use Plot Twist + Augmented Elekk with Fel Lord Betrug and/or Dollmaster Dorian to get a bunch of extra 4/4s both in play and in hand. Given the sheer power of each lackey's battlecry, shuffling a bunch into your deck actually doesn't seem like a crazy thing to do.
Sort of a bummer that EVIL Recruiter ends up far less impactful after you've dropped Dark Pharaoh Tekahn, but it's still a great effect if you use your 4/4 lackey to value trade and then destroy it to get a 5/5 with (potentially) relevant tribal synergies.
This is not a perfect comparison, but looking at Desert Spear reminds me of the discussions around Ray of Frost. A lot of people felt that it was strictly outclassed by other options like Frostbolt, but the flexibility of directing its effect at multiple targets, and other synergies for cheap spells, make it a very useful card that sees a lot of play.
Similarly, Desert Spear is hugely flexible:
It's not a terribly flashy card, but it does enough that it shouldn't be underestimated.
Magma Rager is obviously not a great example, but as others have said this is a good tool for cleaning up Reborn creatures without spending extra resources.
[cardPlague of Flames is a nice card and it's clearly got a lot of Warlock flavor, but I'm not convinced it's all that good.
In combination with Rafaam's Scheme or Fiendish Circle it's frequently a 4 or 5 mana board clear. In most classes, a two-card board clear for 4 or 5 mana would compare pretty favorably to pre-nerf Equality + Consecration and you'd probably see it played, but Warlock has lots of good board clears already.
On top of the fact that Warlock already has lots of good single-card board clears, this combo relies on bad imp generating cards, and Rafaam's Scheme needs to be in your hand for a while before the combo can even be triggered. There are already a lot of potential synergies for these imp generating cards in the form of Jumbo Imp, Darkest Hour, and Demonbolt. None of that came together last expansion, and I'm not sure one extra board clear is going to make them good. Maybe you'll see a few games where this combo clears the board and enables you to play a cheap 8/8 Jumbo Imp, but banking on that seems like a bad idea.
With its defensive statline and taunt, Anubisath Defender seems like a way better Arcane Tyrant. That's fine since it's a class card, and given how often we saw Arcane Tyrant in Druid, I'd expect to see a lot of Anubisath Defender.
The typical baseline for drawing 4 cards in 7 mana (i.e. Sprint), so the fact that Overflow draws one more card for the same mana is already ridiculous. Throw in the healing and synergy with Anubisath Defender and you've got a ridiculously powerful card.
Easily Reno the Relicologist - the "gattling wand" concept and art is super fun, and I love highlander decks and have missed them since Mean Streets of Gadgetzan rotated.
So, this is basically a Master Swordsmith that can't be killed in one hit, synergies with Making Mummies, and slots decently well into Mech Paladin. Seems pretty great, and will easily find at least one archetype to be good in.
Lots of value - spend 2 mana, get 1/2 + a 1/1 and a +1/+1 on death, then another +1/+1 on second death gets you to 4/5 in stats for 2 over time. As long as you can build a decently wide board, this is pretty good, but there have been lots of efforts to make this work and they've largely failed in Priest.
Hard to imagine a deck that wants Generous Mummy. It's a lot of early tempo, but so is Marsh Drake and its drawback is much easier to deal with for classes that want to capitalize on early tempo. The reborn effect might be a boon to keep the tempo going, but making your opponents cards cost 1 less means enemy AoE is coming in earlier to clean up your board. Where this might be useful is as a tech card for aggro mirrors, where you expect your opponent will play out their hand early and get very little benefit from this, or maybe in some Paladin aggro deck that wants to use Rebuke to mitigate the benefit to your opponent long enough to get a win.
I seem to recall Blizzard saying that they don't like the Inner Fire + Divine Spirit combos because it's not compatible with the class identity, but High Priest Amet obviously makes that very easy with Stonetusk Boar. This may be a harbinger for a hall of fame rotation for one or both of those combo pieces - Blizzard has said that they think it's fine to produce super powerful combos as long as they rotate after a few months (this was in a reflection on the failure of the Highlander/Anduin's tenure in standard), so they may be getting ready to give that combo one last hurrah before "hall of faming" it.
Outside of combos, because High Priest Amet's text reads "summon" rather than "play," he does a lot of cool stuff with reborn effects, etc., and after the almost certain hall of fame rotation of OTK Priest, I expect we'll see him used for some pretty serious value plays.
Mogu Cultist is driving me nuts! It seems so ridiculously hard to pull off. I'm not sure I've found any truly good way to do it, but here are some ideas on how to achieve this. The standard shuffle/draw/bounce package each class has access to is Augmented Elekk + Baleful Banker. With 10 mana, the best you can do is shuffle 4 extra copies (Augmented Elekk + Mogu Cultist + 2x Baleful Banker for 8 mana). Tack on a Youthful Brewmaster and you can start to do this in every class. Here's that, and some other ideas:
Diseased Vulture seems really strong - turns every tap into "draw a card, summon a 3 drop" for 2. It's high enough health to hand around after the turn you play it, and has natural synergy with useful Zoo cards like Flame Imp, and to a lesser extent with Demonbolt and Riftcleaver.