Quote Originally Posted by kashi11 View Post
Since I leave cool downs in a separate slot, I can manually pop these to insure they go off. In the off chance that my OGCD skills are up, worst case scenario I lose a few fraction of a second on my next GCD skill in my rotation
This is the order things have to happen for a cooldown to work.
  1. You push the button.
  2. You gain the buff.
  3. The mob's cast bar reaches 100% and disappears.
  4. You take reduced damage.

If you macro your cooldowns, you're more likely to get into the following situation.
  1. You push the button.
  2. The mob's cast bar reaches 100% and disappears.
  3. You gain the buff.
  4. You take the full damage.
  5. Your cooldown fails to reduce the damage from the one hit you really needed it to work on.

The buff has to take effect before the cast bar completes. Those fractions of a second can be the difference between a 14k hit and a 20k hit with a wasted cooldown.