The problem isn't that those dungeons have extra weight in the matching, the problem is most people never bother to unlock the others and /cannot/ pop the other ones because of that. It can only match you with people who all have the intended content unlocked. They could potentially alleviate the issue by simply adding some reward for unlocking and completing the entire dungeon list to make them more likely to pop as more people would have the option ticked off server side, but it would have to be a reward that the players would actually want to go through all of that for....

Aethero really should be in MSQ roueltte, though. That was weird to me all that way back in HW that it wasn't.