What you need to improve?
You have a lot of block rating - this isn't directly bad, but itemization spent better elsewhere.
This link has a bunch of crafted items that would help you - don't buy them off of the auction house, it's generally cheaper to buy the mats and find a blacksmith to make them for you. (And if you specifically find a blacksmith that gets skill improvements from it, you may make a friend as well.) Armor - Items - World of Warcraft
Go farm for Essence of Gossamer - Item - World of Warcraft - it is a great upgrade for you (replace that pvp trinket with it), and as a bonus, AN functions as a decent test of gear and skill - it can be harder there then offtanking is in Naxx10.
Also, you have no enchant on your cloak - there's a couple +defense enchants you can get there as well. Also, farm up or buy Sons of Hodir rep items and get their shoulder enchant. And the engineering gun would help as well.