Y'know, Stubborn Defiance really should top up your health as if it had been triggered whenever you end a fight with SD unused and less health than it would have given you to deliberately let the last enemy "kill" you to get health back.
It's like old tactics games that didn't let you cast heals out of combat so you just had to leave one enemy alive while you heal up. The optimal playstyle becomes tedious because of the game's design.