I am having this issue as well, It is a new save started on 3.03 on the steam version of the game, missing White Marches 2. I managed to get him into my party for just a moment and, as someone else above mentioned, he had a line speaking of "Missing level -1- ability" in his character sheet but it crashed me before I could get a screenshot.
Edit: Welp, tried seeing if getting WM2 would fix it for me. This is the result.