With the cool down resets this is an easier way for SE to keep you from using a CD on class 1 with a two minute timer, switching to class 2, then back to class 1 to reset the timer before the original 2 minute timer had refreshed. The way it works currently is MUCH easier than trying to keep track of all the individual cool downs for 20 different classes/jobs so you can't exploit.

Sure it sucks. but for SE it beats the alternative work/code required.