You do realize that low level roulette doesn't just offer low levels experience, right? While the roulette itself gives you a massive amount of experience for completing it for the first time, it offers level 50s another reward for doing them, which is bonus gil, 100 soldiery tomes, and 5 poetics. While the 5 poetics is rather moot, the 100 soldiery is huge when working on many of the steps of your relic weapon at 50.

Based off of what you guys are discussing in your chat, you would not only denying yourself a faster queue time because you are lowering the pool of people you can draw from(since level 50s can join you in your dungeon) because your logic is everyone should get the highest level dungeon available to them in a roulette, which by nature is "random", but you are also expecting a far more complex algorithm to solve groups in the duty finder than is available or necessary.

This would be a different story if in the future they allowed you to queue together as a group for low level roulette after 3.0 because every current dungeon will be a "low level" roulette when the max level is 60, but as it stands, you are being rewarded as a person who isn't max level by receiving a generous sum of experience for doing that low level dungeon. Just remember that it's only once per day, and that the experience rewarded is vastly greater than what you would receive by killing mobs in your "highest" level dungeon available.

TL;DR version: Low Level Roulette already rewards you significantly more experience than killing in your max level dungeon available to you, and is meant to be once a day. It is fairly balanced as is.