Hey Zblader, here are me thoughts. (I've been going around the Crubicle)
For the cost of 6 measly mana, this card can seriously OP all the other healing cards, especially with Towers, Rustlers, Gnome Riders, Windmill (Not out, but have recently commented on), Soul Catcher, etc. Especially with Soul Catcher and Schrödinger's Cat, this could more or less turn any deck 33% more invulnerable (statistic made up, but my point is what counts!).
However, you have managed the word "instead", so I am assuming that you don't produce any mana at all during those turns, in which case this card is slightly more balanced. You will need to note if you can use cards like black hole, etc.
Having this card in a deck would be better than a shield in that it heals more than a shield would block.
But it is worse when faced in a draw with little mana, especially if your opponent deals a massive amount of damage in one turn (SPARK AND FRACTAL!).
Anyway, it's drawbacks are good.
P.s. nice artwork there!