May be a stupid idea, but none the less something for people to discuss.
What if they made an auto queue system that put you into another queue while you were doing your dungeon? it assembles a group based on people completing their dungeon and leaving group, and puts those people into a group to queue up once again? basically a double LFG system. Even if you can't do another dungeon, it gives people the idea that they aren't far from another person finishing their group and having another chance at getting into a group.
Maybe even a little bit more incentive as well for taking the second invitation for the group. Double gold? a chance at apexis crystals? Double exp bonus for low levels? who knows.
I don't see queue times as an issue right now, but it would be cool to see something of this regard happen to help lower queue times for everyone that feels it is an inconvenience.