This is an issue with queuing for pledges. You get tossed into a dungeon where a group has already completed a boss, why would you bother to finish it? If you get put in this situation I think you should get the pledge completed even if it's only the last boss. This woudl ONLY happen on queuing, so that people can't hop into premades at the last minute and finish the dungeon thereby possibly exploiting the system. People could start paying for groups to clearness dungeons for them to whatever idk. People will exploit anything. But anyway, it seems silly that the dungeon finder would even place you in a group when there's no chance of you completing the pledge. For daily randoms ending up at the last boss I great, for normal pledges it just seems like an oversight.