The CT DF train left without me D:

[Gwaeron]

Yes, it happens a lot. I think the reason is this:

1: Assume there are currently 4 tanks, 4 healers and 12 damage dealers waiting in your duty finder group. That is, two full parties and one party missing healers and tanks. You happen to be in the party missing healers and tanks.
2: A full party (who PFed or something and partied up before queueing up) enters the queue.
3: The new party and the two parties already filled up get the prompt to enter.
4: If they do enter, your duty finder group is back to 0 tanks, 0 healers and 4 damage dealers.

This is extremely frustrating and happens all the damn time, it's not people just withdrawing, because it's always one or two full parties disappearing at a time, not just one member. The other day I queued for three hours (as Scholar, so don't say queueing as healer solves the problem), seeing the alliance missing just one tank and dropping from 5/6/12 down to 0/2/0 once every 20 minutes or so, then slowly building back up, just to drop right back down again... and again... and again.