No, there were others participating (I had already been revived once). I didn't like intentionally sitting out the fight, but once I saw the heal happen I realized that it would be best for everyone if I just stayed out of it after dying again.
Thanks, all. I probably hadn't been as concerned as I should be about Companions, Mounts, and Insignia, although an Epic any of these is going to remain unaffordable.
I've seen other reports on this, and it happened to me as well. The only solution I found was to Abandon the quest and then take it again. The theory in the other reports was that it might have had something to do with running the "Basement" quest, but I scrupulously avoided having any other AI quests active (or even…