Ragnaros - 3/3 after one million turns is so light that actually I always beat them. It needs to be reverted to 4/4 and on 20 minions.
Alex - make dragons T5 and above. Feels bad to get bad t3 dragons.
Rat King - it is just bad. Needs to do something more for minions on a later stage.
Many more, just look at the hero’s play rates.