The problem with queue-ing is you need to go in-front of the dungeon to AFK-queue and peek time to time if you got a party.
What happens instead is, not all people is willing to wait for so long to queue if it looks like there really is no people around so they leave or maybe queue later.
Same thing happens to another player, and another and so on.
This cycle creates extremely long queues.
What I suggest is implement an Instance Queue window like on other MMOs. This should let people queue on any instance anytime. Disabling movement should also be removed when queue-ing, players should be allowed to move while queued.
This suggestion will definitely fix the long queue problems especially for high level players since we are few compared to low level at this stage.