Playing to not fall behind is one thing, and it's not even remotely hard to keep up in this game really. 300 tomes per week, obtained through a very easy manner. The game is timegated, sure you can raid for green drops aswell, but the only competition is from NPCs. I dont worry about falling behind or maximizing my preformance until I set foot in PvP, where a parser wont do jack for you since PvP is dynamic. If you can beat PvE content somewhat smoothly it's good enough for me, shaving off 5 minutes on a raid is hardly something I'd bother with. Because more than likely, the time I would spend to tweak my spec would most likely consume more time than all those extra 5 minutes added together per run.
Limitations are also a big hindrance for min-maxing in this game, there are very few options, both with gear, skills and attributes. You get BiS fairly easy, you learn a good rotation, you learn the boss fights, you stay out of bad stuff on the floor and you profit. It's a trinity game, it doesnt get harder than that.
I can see the parser being useful and legit for personal use, but when you start bringing it to pugs where people are trying to just have fun it should be bannable. If you use a parser, stick to other parser using people, easy as that really. But dont think everyone shares the enthusiasm to have the game as a second job. Also, with the difference in class mechanics/dps design, a parser wont give you a fair answer. Some classes are screwed on moving fights while they shine on static fights, just like other classes have more mobility but deal less damage to compensate.