Close your eyes.
Imagine, if you will, that you have a mage. Ha ha, of course you have a mage. Sometimes I crack myself up. Now imagine that your mage has gear, but that gear is not optimal. Now open your eyes.
Hello, every mage ever.
Yeah, chances are pretty close to 100% that no matter who you are and how religiously you play the game, your mage, beloved though he may be, does not have every slot filled with best-in-slot gear and does not have every item perfectly gemmed, enchanted and reforged so that your DPS is up to its fullest possible potential. WoW is a computer game -- an old one, sure, but still home to millions of algorithms and formulas and computations and other math terms that I don't fully understand. It would take, I firmly believe, a robot from the future to calculate all of those numbers and variables and turn them into something a human brain can parse accurately enough to actually benefit from.
Well, mages and magesses, I have recently contacted Kavan, one of the main authors of the ubiquitous gear optimization program Rawr, and I can tell you that he is that robot from the future. I only pray he can protect us from whatever other, more evil and technologically advanced robot from the future that might at some point follow him through the wormhole with a directive to kill our unborn children or something, because you know that's what's happening.