Do you really dislike playing C'Thun decks? How about Zoolock? Maybe it's Totem Shaman, doesn't matter, this deck has a way to deal with it!
Overall Strategy: Keep control of the board early vs aggro with Doomsayer, hero power, and sticky deathrattle minions like Selfless Hero and Harvest Golem. Against Aggro, freely use the boardclear--this deck isn't a Reno deck, so your life total is more important to conserve. Against other control decks, save them to clear their big turn, and then again to deal with N'Zoth or C'Thun.
In general, as long as each card can deal with more than one card in your opponent's deck, you're winning.
Heroes of the Deck: A Light in the Darkness Tomb SpiderJeweled Scarab In a deck that's trying to edge out both ends of the spectrum, flexibility is key, and that's what these cards are for. From on-curve, but stronger minions to divine shields to such amazing answers as Nexus-Champion Sarad and Bolf Ramsteed, this deck really highlights the strength of the Discover ability.
If this gets enough attention, I'd gladly take the time to discuss matchups in more detail, as well as what you're looking for as mulligans. Also, if you have any questions, comments (positive or otherwise), I'd love the feedback.