This seemed to be a popular theorycraft when Expired Merchant was announced since it enabled a guaranteed discard of Cruel Dinomancer to make it a 5/5 Dreadsteed. Most of the theorycrafts I saw went for a more Zoo-ish approach with cards like Void Terror, Ratcatcher, and Grim Rally. In my experience first trying it though, I found the deck doesn't really want to do that. Spiritsinger Umbra filling your board with infinite 5/5s doesn't mix well with having a lot of minions and you almost always wanted to go for the full board.
Playing around with the deck for a few hours yesterday I only lost a handful of times almost always to hyper-aggressive decks. Antique Healbot and Zilliax may be a good idea to include for more survivability. I'd probably cut the Shadow Bolts and maybe 1 Power Overwhelming to fit them in.