Nothing wrong with that. Just say that your spells only work on the needy. 

I was actually the tank

Using one spell to heal yourself for over 50% of your hp if you're low enough is funny.

That was you!? /s

#NoMercy

The downside to that self healing spell is that it reduces your own healing effectiveness by a large percentage but that single big boy heal is nice, plus if you're a Dragon Knight, you can just use an ultimate and regain a huge portion of your HP/resources which isn't considered a heal as it's a passive skill effect.