If you think you need gear to be able to speed run stuff then you probably don't speed run enough. Anyone experienced enough in a dungeon knows where skips are,which parts to avoid and the fastest route, which mobs can be locked out of a boss room etc. Low level stuff is a cakewalk for experienced players in a group together. The point of that bonus in the first place is to encourage players to help low level players clear content and the main reason for that roulette is an EXP bonus so i think level 50's shouldn't be able to queue together for that one.
It's kind of complex though so i don't know if they'd bother doing something like that where a level 50 can queue with somebody of lower level but not a second level 50.