I understand where you’re coming from, after all everyone doing one mission all the time is really boring. But you need to understand that a lot of players (particularly the more hardcore crowd) don’t see this as a game to be explored and experimented with, they just see it as a math problem that needs to be solved, and like all math problems, there is only one correct answer. This means that if you make every single mission pay out the same amount, there will be one mission that can be finished 3 seconds faster and that’s the one EVERYONE will do to the exclusion of everything else. Until it’s nerfed, then they’ll move to the second-best one until that one is nerfed and so on.
So what do we do about “the white beast problem”? Well PSO2 had kind of an interesting way of solving it, they would have a handful of missions in a rotation and then give them a +100% experience boost, but only one would be available at a time. This meant that if you played every day, you would have to do a different mission each day to Xp because the other missions wouldn’t be there. This didn’t completely solve the problem because it just led to most people just leveling up on the day when the best mission was available, but it did kind of help spread people out a little because people would do items farms on days when they couldn’t XP. Of course there was more to it there, since they had daily quests also that would spread people out and something like that would be very difficult/impossible to implement here since PSU didn’t have any system like that. Something like a random mission being selected each day for an experience points boost could be added I’m sure, which would kind of help move people around but ultimately it’s a problem that can’t ever be truly solved.