Finally it looks pretty stable, both for solo and groups, has not tried partial groups for some time so not sure about that.
However you queue, some fails ready check it tries again some other fails the check and this often goes on 1-3 times.
As you get in front of queue and first an DD does not check, then the tank don't check, should it not be the same tank as got the last check?
Or is it so many queuing that tank get grabbed by another group?
Don't see the point of dropping the group either, just find an replacement, no need for another ready check if you can get an new group up fast.
Yes you might want to drop group if no suitable group is found, say I group for nRoM as DD, now if its no tank who queue for the dungeon or queue as random and have dlc it would make sense to disband group so the other don't have to wait for tank but this is an exception.