Ancalagon
Dusty Dragon
I think any amount of XP loss is unnecessary and makes zero sense. It never did. Does each hit make them temporarily stupid and unable to learn? Is it draining memories and training?
None of that would be "life drain". XP loss for playing the game (you know, doing the very thing that is supposed to earn you XP) is just a very poorly thought out mechanic, and very meta. Which is probably why they dropped it.
Some experiences messes you up, and you come out of them worse off than before. Real world equivalent is PTSD I suppose.