I haven't had any of this @&#% happen with any party member other than tanks.
You finally get assigned to a group after waiting a half hour or longer and as soon as you join the tank just disbands or plays along for all of 10 minutes before suddenly having something come up and leaving.
Tanks being able to get a group almost as soon as the queue up is creating a generation of prima donna jack@sses that cherry pick their random groups as they join them. Sure they may get hit with a 15 minute penalty for leaving early but as soon as that timer runs out they're back in a fresh group while everyone else that got left behind is waiting another 30-45+ minutes for a new tank to show up.