Druids have a glaring weakness: hard removal. Playing naturalize is as useful as playing Millhouse in late game.
Which is relevant, until they acquire Tinkmaster Overspark. Then they get a 3mana polymorph, and hardly ever care if they proc a devilsaur on your minions (still in Swipe range, w00t)
Yes Druids have everything and to a lesser extent so do Paladins, but as others have pointed out it's more of a case of other classes falling behind.
I think Claw shouldn't grant armor, and I also think their Hero Power should be Choose One. But that would slow gameplay down too much. Swipe kind of scales too well, but they need it to be as is; try winning Arena games without drafting a Swipe as a Druid.
My only real, real peeve with Druids that I would make a case for, is the silly amount of card drawing packages they have. Literally something for every occasion and mana tier. But, again, that's probably just an issue with some of the other classes falling behind.