I do like the idea of turning damage you've taken into extra power. Maybe it should be a necromantic skill - do 50% damage to yourself, but give yourself 50% extra damage plus some physical armor (let's say 0.10*lost HP for a start) because you basically bulk up? In my mind the reference point is a kind of power where you literally turn the damage you've taken into physical power, bulking you up as a result. I don't think it should be a Talent though, it sounds better as a skill.
