You know, with COTC causing such issues...
Maybe you should just remove it. All you get are champs who shouldn't be using it abusing it, and creating all kinds of imbalance and broken champs because of it. And honestly, that mastery is such bullshit, I don't know why you added it in the first place.
I would say just re-add SOTA, but take away the healing when at max stacks. Or come up with something new that DOESN'T break everything.