I don't think there really is a change that could be made that wouldn't be unbalanced. They upped the reward for Adventurer in Need last update (not that I've actually looked at what it is now). Unless they added a low chance to get something awesome for it, which is, again, unbalanced, DPS will always outnumber tanks and healers.

My suggestion is to talk to a friend and see if they want to level in dungeons with you. Not that it helps Duty Roulette Low Level, but still. If you want to be a DPS, expect the long waits. It'll come easier once everyone's off the NIN high. I'm leveling my tanks and healers now specifically because I know what DPS queue.