While I appreciate your concern, it's very very very difficult to design a system in which one method of doing something is not better than all other solutions. Given the min/max scene of the medium to hardcore raiding guilds, the build/glyph/gearing combination that returns the highest DPS/HPS/EHP is going to win out consistently. If you can figure out a design strategy that offers multiple solutions that play differently while having the same effectiveness, you should forward Blizzard your resume.

Even if there where multiple talent/rotation options that had the same output the one that was easiest to pull off or had the most utility would still be The One. With a game as complex as WoW it is hard to make multiple builds do the exact same DPS so even if they got close to perfection what was best would just fluctuate with gear and content.

In the past if you didn't just want to be another copy cat DPSer you could play one of the utility classes* (like BC Shadow Priests) but with class casualisation *cough* I mean "bring the player not the class" Blizz are attempting to remove any niche.

* Or for example as I did back in Classic be a support build DPS like the old Mage scorch bitch (to keep those rolling ignites going for over 9,000 damage).