I know that in Rift, you didn't see that many end-gamers actually doing the Random dungeon option, since they didn't receive loot from those low level dungeons that were useful to them. I did the Random dungeon option if I was short on time, just felt like helping a few lowbies, had some achievements I wanted to tag in those dungeons, leveling an alt and wanted to break up the quest grind, ect.
One other thing the Rift LFG reward system has is bonus XP completing the dungeon. If you can add a decent bonus for that reward PLUS first time run reward, it would also help break up the FATE grind to some extent and get more than just endgame folks interested in queuing.
