eh. they won't have any other dungeon unlocked for that class, no matter if they have them unlocked in general or not. if you're say... lvl 30... you only have up to haukke unlocked. you won't be able to queue for anything higher, even if you've done them on a different class that is already 50. did I really have to mention that?

I do statistics for a living. it's working exactly as I said. you will always have a much higher chance to get one of the starter dungeons because the dungeon is decided by the lowest level member of the group.