I thought the solo duties were frustrating...

[Mawlzy]

I'm a casual and I find it very boring. Casual doesn't mean braindead, I just don't care to commit more time to a single fight. You can still have challenging content that doesn't punish your learning phase too harshly and allows you to recover and puts more responsability on personal mechanics instead of body checks.

Is it more interesting if you run it MINE or is the fight design the problem?

I can't relate to the braindead thing, since mine has to be fully engaged to clear MSQ content, at least soon after release.

At the risk of being Captain Obvious, the fundamental issue is everyone does the MSQ combat, and that means there's a huge range in skill level. So unless dungeons come with easy and hard modes, a large group of people are going to be unhappy.