You can vote kick them with some coordination I arranged this the other day when I found someone in the alliance wall running with their original stoneskin timer in the base over halfway through the match. The people in their party couldn't kick vote and thought it wasn't possible, I just advised them to hold a few seconds after party wipe till no one was in combat and that worked. Plus getting people to try an approach where they didn't run back out to die one by one was useful as a side benefit.