I wonder how many other classes will get similar cards. We have armor and heal (Warrior/priest), which class would be most likely to get "deal 5 damage" if your C'thun has 10+ attack... or maybe it'll boost another minions attack/health (options).
Overall looks like it'll make C'Thun priest decks a little bit better by giving them some synergy. 20 hp heal with brann (who you'd probably want for the other c'thun buffs as well).
I'm just another one of those. You know, those who do things. Things that need to be done by those that do these things in order to do those things that don't do these things themselves. Has the word 'things' lost meaning to you already?