I think a Mythic for dungeons would be fine maybe even just limiting it to lv50/60/70/80 dungeons. The rewards wouldn't even need to be that great a title per dungeon, some form of glam pieces here and there and a mount for competing a lv series. So finish all the lv50 mythic dungeons get a mount, lv60 get a mount, and so on.

Also also don't put then on roulette if ppl don't want casuals to have to be carried. If you want to run Mythic you have to form a party.