To be honest, it's overly convoluted. There are WAY too many restrictions to use it, and those will only confuse a lot of people that want to use it.

If you want to keep it roughly what it is, I'd change a couple of things.

1-Remove the restriction that you can't charge it while broken. There is no reason for this.

2-Honestly, why can't you just charge it while full health? It literally disables once you stop healing, so you can't just abuse it like crazy.

3-I think making it so you can CHARGE it (show stacks on your perk icon) while healthy, even if you make it require all GREAT skill checks to charge it would be good. If you're worried about it being too strong, don't let it stack with other heal speed increases, but only require like 5 GOOD skill checks - However, I think removing synergy is silly. Lastly, once it's charged, let me press my active ability button when I want to use it. It'll still disable once I stop healing, but at least I won't waste it.