Stopped reading when I saw Seiryu in there because he isn't mandatory for MSQ progression.
The MSQ roulette is staying as it is for a while, along with the 2 dungeons staying in the Mentor Roulette. The rewards for clearing it and helping other progress through the story are rewards that many still don't want to pass up and take for granted.
As far as Mentor Roulette goes, I'd rather do Castrum Meridianum or Praetorium than an EX primal nowadays because I can CLEAR these 2 dungeons and get a win from the mentor roulette, despite the unskippable cutscenes no less. People are still careless in doing EX primals via duty finder synced, more so being unprepared for mechanics being explained and being undergeared for them in several areas.