I once ended up in a dungeon with a tank who seemed to be a (nonfunctional) bot. Didn't turn stance on, didn't dodge, didn't respond in chat, didn't react to anything, just walked ahead vacantly. So the ninja became the tank. I don't think we even vote-kicked the bot. It was a while ago, so the memory is vague, but I think we just let it stay while we effectively did a tankless, 3-player run of the Stone Vigil.

That's how I discovered that I prefer unfortunate incidents over proper dungeon runs.