I think a good compromise is that your minions can only deal damage as high as your tavern tier, so if you're tier 3 and you shifter (or galakrond) into a t6 minion it still benefits you in the long run but not so much as doing stupid amounts of excess damage. A particularly egregious game I encountered was when I was facing AFK on turn 4. She picked shifter and it turned into imp mother. Imp mother then proceeded to spawn 2 malganis and the 3/9 void taunt minion. (I attacked with my first minion, imp mother hit my unstable ghoul and procced, then procced on ghouls death rattle. Took 23 damage on turn 4 as Eudora. Never had a chance to recover. But with that being said I never really considered the tavern tier on minions to be that bad outside of a handful of egregious offenses, and feel like extending the game by even 3 turns will make most builds obsolete. Even divine shield murlocs with poisonous would pale in comparison with a macaw/swiper/goldrin build if it got to the point where the swipers were able to kill 3 at a time, or if a dragon build has enough time to triple a kalecgos and double up on nadinas.
I think a good compromise is that your minions can only deal damage as high as your tavern tier, so if you're tier 3 and you shifter (or galakrond) into a t6 minion it still benefits you in the long run but not so much as doing stupid amounts of excess damage. A particularly egregious game I encountered was when I was facing AFK on turn 4. She picked shifter and it turned into imp mother. Imp mother then proceeded to spawn 2 malganis and the 3/9 void taunt minion. (I attacked with my first minion, imp mother hit my unstable ghoul and procced, then procced on ghouls death rattle. Took 23 damage on turn 4 as Eudora. Never had a chance to recover. But with that being said I never really considered the tavern tier on minions to be that bad outside of a handful of egregious offenses, and feel like extending the game by even 3 turns will make most builds obsolete. Even divine shield murlocs with poisonous would pale in comparison with a macaw/swiper/goldrin build if it got to the point where the swipers were able to kill 3 at a time, or if a dragon build has enough time to triple a kalecgos and double up on nadinas.