I actually hate parser's. I feel like it takes the fun out of playing a game, and often fosters a negative competitive, and at times, even an elitist attitude towards other players or classes.
Not to mention, all classes are not created equal in terms of dmg output, so all a parser really does in my opinion is measure how much your character's damage was and give the highest dps some bragging rights. (Which is pretty much the same concept as measuring e-peens, isn't it?)

It's just my opinion though, I could care less if it was put into the game, I just wont like eventual negative side effects it would have.