The lack of variety in competitive decks is what drove me away months ago. I recently came back and have been dabbling here and there. The biggest thing I've noticed is that it seems like people are playing a much wider variety of decks in unranked games. I haven't touched ranked games since I got back into it. I'll probably just stick to unranked games.
I'm sick of facing the same build daily without a curveball here or there.
Mage = mech mage
Hunter = deathrattle aggro
Warrior = control warrior
Warlock = zoo or handlock
I really like watching Kripparrian or Noxious because they do some crazy, fun decks that are also competitive (usually). I want the next expansion to really shake things up.