Here's my take on parsing personally. Everyone pay's for this game monthly, you pay month by month. In 30 day you should be able to make notable progression, whether it be light raiding or hardcore raiding what have you. Parsing numbers helps maximize your play time because you don't waste time trying to figure out your rotation on looks alone. You break it down in numbers so you can see where you are weak at in terms of your actual rotation. In that regard you then take those fundamentals and apply them to raid mechanics. You reduce your marginal error and therefore maximize your numbers in combat, in doing so you reduce your own chances of wiping. Meaning less time wiping in raids = Time well spent.