First things first. There is no defense cap.
Now, looking over your gear, here's my thoughts.
Your armor looks good, but could be better. Consider buying http://www.wowhead.com/item=47735 and using it in place of the dodge trinket.
Your hit rating is on the high side, your expertise looks good.
Avoidance ratings are fine.
Your gemming needs fixing. All gems should have a stamina aspect to it, so blue, purple and green are the colors you should use. I consider only socket bonuses of more then six stamina per offcolor gem to be worth going for. I see six yellow or red gems in your gear - even if you keep the socket bonuses and replace them by their green and purple varieties, that's another 1k health for you. If you go all blues, more.
Since you'll lose hit and expertise, going all blues may drop too much of the stats, so find out what works best for you.
Your defense is high enough, so those defense enchants are rather suboptimal. Put 275 health on your chest, armor on your cloak and the pvp stamina enchant on your shoulders, they'll all get you further.
After you make those changes, see if there are any stats you are lacking that you need to enchant for - my advice will make your hit rating and expertise drop by quite a bit, but threat shouldn't be much of an issue anyway. (Remember - that's what hit and expertise are - threat stats.)
I don't know much about warrior prot specs, but yours looks fine to me.