The roulette system is just as much a valid target for criticism as any other part of the game. That it's designed to fill queues doesn't make it special and doesn't really have anything to do with the issue being brought up. The only kind of change that is going to be problematic is one that prevent roulettes from achieving its dungeon filling purpose. Attempting to bias roulette results in a certain way is not such a change.
This element will always be there, but it is trivially easy to influence the weights of different outcomes. The most obvious one, and I'm using this for the sake of example here, is a blacklist that totally prevents a selected a dungeons from being accepted as a roulette outcome. If a player had the option to blacklist Sastasha and did, then that player would never see the dungeon in roulettes even if the rest of the data center was queuing for it.The randomness in essence is on what duty a number of players are going for at the time you hit the queue button.
A more realistic option may not involve completely removing duties (although if the pool of roulette participants is large enough and have diverse blacklist options, the problems vanishe) but instead do something like shuffle the order of participants in the queue to help them get into duties they prefer. The roulette system already has some capacity to do this because you already can blacklist dungeons by not unlocking them or by using one of the multiple roulette options to avoid certain content (no Sastasha in Expert roulette for example), so this doesn't even require a rework of roulette outside of new UI.
That defeats the point of the forum though. Asking for roulette improvements is perfectly valid, as is asking for any improvements at all. I don't understand why people seemingly forget that so often when this topic is brought up.Either you accept it or find something else to get your tomestones from if it bothers you that much.