Hearthpwn

you first need to go to "all cards" to even see wild cards, have you done that?

This is true, however paladins heal synergies are already reliably usable. The point still stands that this card does not impact the board at all. The full heal is nice, of course, but this card doesnt defend you. Shrink ray, consecration equality, pyro equality, they have all been around forever, Let's also mention that pally is losing Tarim, another strong tool in control decks (not just aggro). 

We're still at the same point as when the last expansion released, tools (some of which are better than others) that could build a control deck, but individually don't do much. On top of this, the deck still doesn't have a win condition (Uther is leaving). The full heal won't save you from aggro either, it may buy you one more turn and in fringe cases will win you the game, but a lot of the time after you play this your opponent holds free reign to do whatever they want with the board they just used to bring you low. 

Don't get me wrong, I'd love for a control/heal paladin to be viable and I think it even may even have a shot to be strong (depending on the cards that get released), but not with this card.

People comparing this to tree of life are right, it's a lot like it. You do get a 4/12 body for 1 mana extra, but just a 4/12 won't cut it. This card won't see play unless you can confindently and consistently give it taunt