I'm not sure. Is there a penalty for leaving a group when someone has already left? I've sat in a dungeon for 20 mins waiting for a replacement healers before now and in the end the group just decided to Vote Abandon rather than just have people leave piecemeal and some poor sod dps who had been in the queue for 14 mins find themselves in a group that was going no where. Frankly there aren't enough people who tick the 'join group in progress' box.

Removing Group Abandon at the moment will probably mean sitting around for a lot waiting for your group to refill with people continually bailing cause half an hour penalty before joining again is better than sitting around for half an hour for new players.