EDIT: Major re-do on this deck, the first one was way too slow
You may switch one Shadow Word: Death for Entomb if you want to. I chose only to include one Entomb as adding cards to your deck might not always work out that well when you are looking for one specific card (namely C'Thun).
Make smart trades. The fact that you need to control the board in order to survive until you draw C'Thun doesn't mean you should trade blindly everything your opponent throws on the field. Use your removals on particularly sticky/troublesome minions.
You should mulligan for Northshire Cleric and Beckoner of Evil. Only keep Power Word: Shield if you have either of those two. If you have The Coin, you can also keep Twilight Elder or Disciple of C'Thun.
Feel free to comment anything you want about the deck.