Your gear looks good, but your gems seem a little random. AP/Stamina, AP/Resilience and Defense prismatics.
Since you seem to be comfortable with your survival and want to increase your DPS, I'd suggest gemming for hit and expertise. You're almost at the hit cap for yellow strikes right now, so I'd focus primarily on expertise. It'll increase your DPS by turning boss parries and dodges into hits. This has the side effect of reducing burst damage you take when a boss parries you. This will make your healers' jobs a lot easier.
Red and Prismatic Sockets: Precise Scarlet Ruby - Item - World of Warcraft
Yellow Sockets: Accurate Monarch Topaz - Item - World of Warcraft
Blue Sockets: Guardian's Twilight Opal - Item - World of Warcraft
Drop Precise Dragon's Eye - Item - World of Warcrafts in blue sockets, then yellow sockets. Ideally, you want to be gemming almost purely for expertise.
This creates a problem in that it would take you below the critical minimum of 540 Defense. I suggest addressing the problem by replacing some of your current enchants with defense enchants. You can pick up an expertise enchants while you're at it:
This should increase your DPS by preventing boss mobs from dodging and parrying as often, while keeping you uncrittable. It would also help your tanking in that you wouldn't take as much burst damage from parry haste.
I should probably check to find out what exactly the parry-cap and dodge-cap for expertise are, but I haven't been able to track down the numbers when I've looked for them lately. I'm pretty sure the above won't get you over either cap, though.
Hope this helps. Two quick things I noticed: you were sitting exactly at 540 defense on your armory. Just in case you don't know, 540 is not a cap for defense, it's a minimum. Defense is still a valuable stat--I'd say the most valuable stat in most situations--after 540. Also, i's my understanding that for warrior tanks who choose to gem for straight-up DPS, Strength is preferable to AP because Strength also increases your block.
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