No you wont (if we speak client side only) because its not like you are allowed to grab anything you want from the server, its right there in your links. What client does is literally asking the server "what are the stats of my character?" in this case only changing the way server responds to this question is a viable solution.
Buuuut just for shit'n'giggles... theoretically what you could do is calculate the critical damage rate basing on the damage dealt, but then again this would require dealing the damage multiple times, it would have to be same skills/items/target etc etc - not worth it