Having an option to join a specific group might be too abusable, but I'd love to have the option to say "join only parties in progress" to the DF at least.

Recent personal example: I was running a level 50 roulette the other day (partly to get an alexandrite map since I was working on the kettle quest) on DRG, since it could use the EXP. Ticked in-progress so that maybe it would queue faster. I got into an in progress dungeon where both the tank and a dps had bailed. We sat there for several minutes waiting for a tank to show up, calling out to linkshells, nothing. Eventually I decide that since it would probably easier to find another dps than a tank, and announce to the others that I'm going to leave and try requeuing as a tank. So I requeue for the roulette with in progress checked. I figure, I still need the actual roulette, and I'm either going to get paired with the same group or with another group that also needs a tank to fill in, right? Nope! Queue pops for a new instance. It's possible that another tank showed up to the first one while I was outside, but I doubt it.