The cap is with relation to dodges, from behind (as they pertain to rogues). The parry cap is significantly higher.
The procs on all of them necklaces, from initial testing (yes, I'm exalted with SSO on PTR - don't ask
) seems to be roughly 15%, although I need more time to do a proper sample size. It's 10secs, with a 45sec cooldown. It's still pretty good considering it's rep quartermaster gear (look at the other factions!) but obviously is going to be outclassed by higher level raid gear, as is should be.
p.s. If anyone has a decent way to parse a combat log for proc rate calculations, I'm all ears. Right now I've been doing it manually, and it's a complete pain. Procwatch etc are understandably choking on PTR atm.
Edit: Changed rep reward to quartermaster gear for clarity and to differenciate from rep rewards like Karazhan/Hyjal rings.