I've had fun but they are not fun based on difficulty or mechanics, same is said of CT/ST. They are kind like the point and click smash everything get loot gameplay (think Diablo, MMO style). Which is fun in its own way for what it is. Blow things up look at the pretty scenery, get your rewards, rinse and repeat. It is a type of gameplay (enjoyed by some not by everyone) and it isn't meant to be interesting based on difficulty.

If you enjoy complex fights and mechanics that's where the coil and primal lines come into play. And those fights are very accessible to those who would like to do them.

I do feel like there's a missing spot for complex difficult 4 man content but I think the devs are just not focusing resources there since that option exists in the form of 8 man content. I'm not saying I wouldn't like to see it but due to the overlap it probably isn't high on their priority list.