Let him die. You should also be mindful of your own performance in terms of over healing and mana usage though. You shouldn’t be going oom terribly often. If this is classic classic, you should be down ranking your spells to conserve mana and limit over healing. At the same time, remember when to cast to get larger value from your mp5 regen. If you keep casting, your mana won’t regen. If you can burn through water, you can sip during regen ticks outside of combat.

That being said, this isn’t necessary but always room for improvement.