Hearthpwn

I keep Luckysoul hoarder for my early drop as he can shuffle 2 soul fragments into 4 mana clear board with Shardshatter mystic.

You can replace Malicia for Cycle of hatred if you want but in this meta i prefer having wide board of 3/3's instead of rush, although it doesn't work for big minions like the one from Libram of Hope.

I didn't put Kayn because if you want to remove taunts 1 mana silence is better than 4 mana charge minion although i haven't tested it as I don't have him. Put him instead of Consume Magic.

Yl'gnoth is really nice but only with Warblades equipped. 

As I was losing hard against rogues I would add 2 one drops (i was playing without them) for 1 chaos nova and 1 consume magic. The best choice is Spirit Jailer.

Mulligan guide: 

always keep: Spirit Jailer, Silent Watcher, Luckysoul Hoarder. Early drops are really imporant for later dps into face.

against Paladin: keep Consume Magic, Soul Shear, Eyebeam - one of those. You can also need Chaos Nova in case it's ramp paladin

against Rogue: keep Ooze (really important, If you have two oozes you can keep one as an early drop. Use it when he buffs weapon if it's a weapon rogue. Use immidiately if he plays Self-sharpening Sword),  Shardshatter Mystic with Spirit Jailer or Luckysoul Hoarder. Do not keep Chaos nova as it's really slow., Aldrachi Warblades

against Priest/Mage/Warlock: keep all weapon/hand dps as possible, Yl'gnoth (best with Aldrachi Warblades), keep Skull of Gul'dan

against Druid: keep Chaos Nova, Shardshatter Mystic + Spirit Jailer or Luckysoul Hoarder.

against Shaman: I don't really know, I haven't seen much of them, anything is good against shaman

against Demon Hunter: keep as much lifesteal you can, You will also need draw and soul shards.

against Hunter: I'm sorry, This is really hard matchup, depends on what secret he plays