Depending on the dungeon, and the players, I like to just continue clearing. Most things can be done minus a tank, or a healer. It makes for some fun playtime.

One moment that sticks out, there was a healer that “mysteriously” disconnected after a tantrum. At the beginning of a DF run. Our party just kept chugging along slowly, during which time the healer came back online twice after the initial disconnect, the final time they went on tirade with all sorts of expletives at us for not kicking them. We managed to clear to the last boss, before we need to find a replacement for our offline party member.