4/10 for 4 mana? That's a full blown Twilight Drake. Wow. Alas, you will rarely get the effect on turn 4, tho. Even without it it's still a Yeti and will never really cost you a game or anything. Since C'Thun also gains attack when he is dead, you will trigger her eventually. Pretty solid overall.
Druid can't have hard control decks, they have no removal.
what are you talking about? this is the classic example of a good midrange minion with an insanely strong potential upside. with all the Naxx deathrattle minions and Shredders gone, Yetis might actually see play again.