Some PAIN updates:
1) I can definitely confirm that you can avoid Nok Nok and jewbelost getting gibbed by the FoD by pumping Fort (if you don't have the gear, just install the cheat mod and increase his fort to 32 temporarily)
2) Octavia and her bull are fine quest-wise, did not have to resort to save-loading or anything, as well as Harrim
3) Magic negro is either bugged or supposed to die if you allowed him to gib the giants (not that I really need him, but he still was better DPS as compared to other choices except nok-nok)
4) Arthas seems to be unrecoverable - he and Jaethal both kill each other, but for some strange reason you can resurrect her, but not him. I even threw her under the elven bus, but she still appeared in the room and killed Tristian. It seems it's impossible to trigger his final quest - devs confirmed here:
https://steamcommunity.com/app/640820/discussions/5/1735468693699721546/
I tried finding the triggers in DB files, it's simply missing from saves.
In principle, I can make do with Harrim, but his stats are kind of bad, he has 3 times less healing as compared to Arthas and worse compliment of offensive spells. So I'm probably holding off the game