Back in Everquest 1, I remember my guild leader got hold of the very first dps parser I'd ever heard of. He used it during raids, but didnt share the information in the guild, only posted it on a forum called Steelwarriors or something like that, to discuss with nerdy people :) Anyway, that dps parser was the thing that turned me from only playing for fun and the best I thought I could play, to looking at maximising my dmg, and minimising downtime. I was in an endgame raiding guild in EQ. That meant raiding 5 times a week atleast, and sometimes getting up to contest spawns with another raiding guild - literally racing to see who could muster first. These people were pretty hardcore. Then Enter the dps parser. - And the min/maxing. It completely changed the way I aproached the game. - Granted in EQ there was a significant amount of awareness and skill required to manage agro - personal responsibility being an actual thing. As well as the game actually calling you out for failing to do this: You will not evade me "nameoftoon" - broadcasting to the whole raid who was a moron. Anyhoo, my point is, once the dps parses became public, AND the agro management became trite - AND awareness was something the UI did for you with big fancy warnings and color codes, all that was left for the player to do was manage a rotation. - And that funnelled everyone into maximising for highest output be it healing or dmg. And that meant funelling everyone into the same or very similar specs.

I believe you could reverse this by bringing back the other skill requirements. CC - AGRO and awareness, and removing the parts of UI that manage those things for players. Im just not sure that people who play MMOs today would find that fun.

So as to your question. It was players who introduced the dps parsers. And opened the door to the development of the one trick ponies. You cant expect developers to put that cat back in the bag for us with any success. And now you have a whole generation or two grown up with playing these types of games, and I doubt they'd find the learning curve and punishment for failing to be good gameplay.

And btw I dont believe that EQ had diversity in builds, because we all got pretty much the same AA, the diversity rested on strength of the toon, in AA amounts and gear. How people wove their abilities together, and how agressively they could play within the other areas of skill; agro room and raidawareness - was what seperated the apples from the oranges. - Not numbers on a list.