Using low level Duty Roulette as a geared 50

[Orophin]

Well something is wrong about scaling.
Why use the roulette if < lv 50 grinding exp once done with the daily bonus (except if you're a tank, the most predominant needed class on every roulette, extra bonus) if the amount we get downscaled is not growing accordingly?

There's really no point. The best XP you'll be able to get is from doing a level appropriate dungeon once you've gotten your XP bonus for the day. The problem is the roulette pops pretty fast, but will more often than not dump you in a low level dungeon, versus the long queue time for a higher level dungeon with better XP.