the quests for the classes...
I cant refer to all of them since i tried only a few....mainly priest,warrior & mage...
While at first it seemed cool, those quests support the worst kind of gameplay hearthstone has to offer. They follow the same mechanic as dragon priest, anyfin paladin, cthun decks and so on. You just stall all game long, play defensive and destructive and get rewarded in the end.
They could have been more creative. I mean as soon they pop the quest on turn 1 you know 95% of the cards that will come.