I think a big chunk of XP from the entire Doctor encounter is supposed to be cut off from you if you're not traveling with Lohse. It's probably possible to force a fight and get most if not all of the XP, but I mean it's only natural that you miss this chunk. Haven't done a playthrough without Lohse so I'm not sure though.
I got to Arx when I just barely hit level 18. The early encounters outside the city are level 18, so it hasn't been a big deal. Now I'm trying to scrounge up another 100k XP for free somehow just so I hit 19 and can go ahead and do the big fight in the sewers. I'm definitely underleveled - I skipped a few big fights on Nameless Isle - but could also be that it was intended that you need to explore for a good while for free XP before doing much combat.
I don't mind being cut off from one or two big chunks of XP, as long as I'm not punished too heavily for that. Especially if it's easy to miss said chunks. That's just how it is when you have a lot of options to resolve things.
Last edited by Try2Handing; 01/10/18 08:33 PM.