Deck i've played on stream to Top300 Legend on april, 26th.
Hunter is problematic every other matchup seems winnable.

against control decks we have Medivh and Jaraxxus which generate insane value.
against agressive decks the cheap early minions stop the bleeding, we then clear the board once and should be in control from that point on. Also running enough heal to beat pesky decks like Pirate Warrior.

Mulligan:
always keep Bloodbloom. If you have it already can keep Violet Illusionist and/or expensive spells as well.
if you dont know what your opponent plays (Warrior, Druid) assume its aggro.
vs aggro keep all 1-drops except for Voodoo Doctor. can keep Tar Creeper if you already have sufficient early game. also keep Hellfire in most situations
vs control keep Twilight Drake
vs weapon Warrior, Paladin keep Ooze
vs Rogue, Mage keep Dirty Rat

good luck =)