Well this isn't great news but it's good to know.
WoW Forums -> Natural Perfection and Resilience
The most you can reduce a crit by is 25%, and natural perfection counts as part of that, so beyond a point (something like 300ish) you stop getting the benefit from the crit reduction portion of resilience.
This means at higher levels of resilience you'll want to take points out of natural perfection and put them elsewhere (unless you really like spell crit I guess)