Sooooo, how in the world are you going to not stack SS if you need it to be at 490 to be at 2.0sec GCD ?
You stack SS to 492~497 and then you use crit....which is a CHANCE to crit. This is not over 100 times, it is EACH hit has a % to crit. The same as with melding. Just because you have 40% chance to successfully meld an item doesn't mean that you will have 40 successful melds every 100 tries. This game doesn't work that way.