Everol

Have the same issue as well exactly as you describe it; the loading issue in the two zones and party swapping issue. The only way I can get party members to reliably swap out it to remove them, get out of the hireling screen, go back in and then add someone else. This however still does not work with Kana, furthermore I find him showing up randomly as I travel around. I did notice before I took him out of the party the last time that he had multiple copies of the same chant sequence (like 4 chant A's) and they were very screwy. He was naked at the inn in the first twin elms zone, and then I found him later fighting a horde of NPCs in the Paths of Old Nua by himself (unless this is part of the story?)

I have the same issue, made another chanter to replace him but now I miss all the dialogue etc...