No comment on mental but there's a guy in my fc with cerebral palsy who has to play one handed. He is able to clear the solo content without that much issue.

I feel like this is a bad idea. The instances as they are barely ask anything of the player. If you know how to play your class and aren't horribly under geared, you should have little issue clearing msq content. I'm still confused by people who had trouble with Zenos. I cleared him first attempt, and I'm not a savage raider or anything. There was one player I remember who couldn't clear I think it was Zenos, and it turns out they were just spamming riot blade.

I don't think its too much for the game to expect you to understand how to play your class on a basic level 100+ hours into the game