I'd be surprised if Xykon hadn't invested a lot of money on protective equipment. He probably took less than the nominal damage.

plus, all characters tend to resist much more damage than they should, according to raw. Take for example roy vs thog, that should have ended in a couple of rounds. And V takes against samantha a maximized ligthning bolt, whose reflex dc was failed by haley.
I already theorized that in ootsworld hit die are maximized. That, or rich don't really care to keep an accurate hp count