Mulligans
General Mulligans
Ideally you want to get the scrap imp down as early as possible so you can later swarm the field with buffed felwings and others.
The cultist is optional, but I think it can work nicely if timed correctly, especially with the Demon Hunter's prevelant aoe. Even 2-4 1/1s can quickly become a monstrous field with Teron Gorefiend and/or Fiendish Rites.
Combine Zoo and handbuff warlock to create a genuine monster capable of slaying any deck.