So I noticed something strange when checking my fight history today:
https://i.imgur.com/5ZlaaGO.png
As good as the xp is, and as much as I would want to have earned about 18,000 times the total amount of xp of all bots in the history of this game, I think it's a display error :p Also of note is that several of the other xp values around these seem to be erroneously low. For example I definitely would have got more xp than 10 billion from 34 fights at level 274. Possibly relevant to the issue is I was using a hastened adventure buff during these particular fights.