Edit#2 I altered the deck a little bit by smoothing its curve out which I did naturally on hearthstone, but for some reason on this site it was denying me to edit the deck so it has been left unchanged for a while.
I think that this deck is legend worthy because of my 95% win rate, and because I have constantly been ranking up.
I have ranked from rank 14 to rank 5 with it. The main problem is super face shaman which will wreck you if you draw bad. Every other match up including mill has been a massive victory for me though.
EDIT (I Removed the nerfed Druid cards out of sheer anger, and protest.)
Once the rest of the set comes out I will try to replace the nerfed cards, but I might just switch classes and that is just sad.
This is how I think a good C’thun Druid deck will look. I plan on building this deck when the new expansion comes out as well, but they could nerf some of these cards such as Ancient of Lore. I also left a few cards out such as Big Game Hunter because I think they will be nerfed.
If none of these cards are nerfed then I can see this being a great deck, and you could easily make some changes to it such as switching the wild growths for more C’thun directed cards.
I also have a lot of 6 drops because I think Mire keeper can regularly be played before turn 5. I also added in Brann to give a better chance of getting your C’thun to 10 attack by turn 4. Depending on how much silence is needed you could think about removing the keeper, but I still feel that it is a staple in druid decks.
Whatever happens I think C’thun decks will be in the top tier of standard play.