Making auto attack the primary source of dps would have a HUGE impact, and many peoples performance would go up because automated combat is lazy.
And this is a problem... why?
Right now with WoW's current system you can have 2 players in identical gear putting up drastically different numbers. In a system with mainly autoattack that isn't the case anymore. The guy intently watching the fight would be doing basically the same thing as the guy in the other room making a sandwich, or throwing another load of laundry in.
No. The guy watching the fight is doing the same DPS as the guy doing his laundry. He's not winning the fight, because winning the fight should not be about doing the DPS.
Right now you still have to work, and earn your place at the top of the meters. A quick read of icy veins isn't going to make you world first material, or even close to it.
Because winning the fight is all about doing the top DPS, and not doing the top DPS makes you lose the fight due to the enrage. Am I right?
Side note: People are talking about non-set rotations, which is something that's different. When I was playing, the rotation was all about the routine. Place these three dots in order, repeat casting this spell until it's time to refresh dot #1, then cast, then refresh dot #2, and so on. It had zero decision, it was all about how well you mastered the routine. Then, the difficulty was you had to react while maintaining this routine, and failure to react led to death, and failure to maintain the routine... well, led to the enrage timer, and death.
Anyway, to summarize the thing about good vs bad gameplay: If your gameplay could be performed better by an add-on, and the only thing preventing that is because the designers decided to lock that function, then it's not a game, it's about imitating a robot, and how close you can get to it. Which, I supposed, some people like.
It's about being a gamer vs being a player. Do you want to play the piano, or doing a game?