C'thun Dragon Soul Shard Quest Warlock

With Madness at the Darkmoon Faire, control decks will gain a new strong control tool in C'Thun, the Shattered, and in my opinion no deck will be able to utilise this better than Quest Warlock. Not only does the deck draw quickly enough to actually put the Old God back together, Lorekeeper Polkelt allows you to put him on top, after which you draw it with the hero power and make it cost (0). Follow up with Alexstrasza next turn and the deck will have gained a new finisher, which requires a lot fewer set-up card than the old Malygos win condition. This allows you to put more survival tools in the deck, improving it considerably. At least, that's the theory.