I really think it's a little OP, considering you only spend 8 or 6 quanta to heal yourself to 100/max health. I believe the card should stay 2 or 3 turns before you can activate its cost.
I thought it is OP too, but it needs two turns to activate, it can be destroyed or stolen then, that's why we should not compare it to miracle with high cost, yes, but with instant effect. However, to balance it better, I would suggest healing 75% of taken HP, I mean if you have 20hp left, it would heal to 80hp, or if you have 80hp it would heal to 95hp.
Also a question about unuuped one. If your max hp is over 100hp and you still have over 100hp, does it do nothing?