I think WoW's exclusive concentration on mythic dungeons and raids has lost them a lot of players. You can see it in the changes they are implementing now, they are trying to shift it back again a bit. Why would they do that, if the numbers would'nt suggest it to them? I think what had worked better in WoW were the old hard modes (the ones before the mythic system was introduced not that step in between). But you'd outgear those too.
I can understand your need and wish for recurring content you find challenging. I applaud, if people with different tastes get their wish. But i think SE still will need to find something beyond msq content to do that. Because, if people (not necessarily you, you seem more nuanced) get their wish there, it might simply render the game unplayable for people below a certain skill level and for all I can see, SE doesn't want that.
Maybe they will build up on the criterion dungeon idea, make that more flexible, so it cannot be predicted as much and then have it as a roulette. I, personally, think, that is one of the better ways, since experienced players will always learn encounters fast and if they know them, they will be trivial to them. I don't think there will be any good ways to aleviate this other than making instances unpredictable. For me, these criterion dungeons seem like a test right now. I can be wrong, though.
Another thing along those lines is the duty-support I percieve as a fall back or safety net. Maybe this will someday cover all of the msq and then, you can always experience the story and the other things can be a bit more flexible.
I am not adverse to job-changes (or role changes). I just think it will always be hard to satisfy demanding players and not overwhelm struggling ones with the same content.