Your immediate goal needs to be getting over 490 defense. No doubt you already know this. Most of your gear looks fairly solid (and you've had more luck than me with shields, only seen that shield once on my holy pally alt D: )
I suggest you check out some of the guides here on TankSpot, there's a good pre-Kara gear list in the Theory, Articles and Guides section of the forum. While you're there, you should also look at some of the other guides, there's a lot of good stuff there. As for what you should immediately replace, I'd suggest getting a new chest and rings. [item]Andormu's Tear[/item] is good until you get something with stamina on it. [item]Breastplate of the Warbringer[/item] from a Nagrand quest chain is good as well. [item]Grom'tor's Charge[/item] from the Cipher of Damnation quest line in Shadowmoon Valley is a good, high stamina tanking weapon too. You can also replace your belt with [item]Sha'tari Vindicator's Waistguard[/item] from the Arcatraz key quest line.
Aside from that, take a look at the guides here and go from there. Good luck!
Edit: Forgot to suggest a belt.