I only played it for a very short time, but cata affliction seemed like a well enough designed spec.
Demo and destro on the other hand absolutely needed to be cleaned up. Even then, I think destro was the only spec out of the 3 that was really well designed. Affliction was fun because it was overpowered and dumb simple to play. Demonology was the epitome of hard to learn easy to master and was extremely convoluted to the point where I have a hard time calling it a well designed spec.
Frankly anything will be well received if it performs as well as locks did all of mop.