Critical has been made complicated my friends; more so then you would think. If you had 500 critical you wouldn't have perfect critical. It will take some time to explain so bear with me:
Much like figuring out pet resists, critical is not simple math. Some of you may know that 10+5=14 in pet resists at times. How does this relate? Critical works in much the same way. The only true way to recieve maximum critical ( not even positive about this ) is to have a piece of gear with 500 critical by itself. Now there is no way to test this, since there is evidently no piece of one gear with 500 critical in game. Smaller parts that add up to larger numbers of critical are not criticals as often as one piece of gear with the same amount of critical as the others add up to, this part I do know. For a real world example, this is like saying instead of 1+1=2, its saying 1+1<2. An in game example would be someone with 90 critical from the hood of espirit, and the cape of espirit would have less critical then someone with a wand that gives 90 critical by itself.
The difference I have not calculated yet. It may be a fraction of a difference and not really effect anything. It may be a large difference and something to keep in mind going forward. I find it pretty interesting.
Actually if you divide your critical rating by 5 you will roughly get what your critical percentage is. 500 IS almost perfect for critical. If you roll your mouse over your critical rating it will tell you your percentage. How I got it was dividing my critical by the percentage it the answer for every of my critical rating was about 5 so I've drawn to the conclusion that divide your critical by 5 and you'll get a rough estimate of your critical. (No 100% guarantee everything here is accurate - critical rating is a peculiar thing)