Drop Imp revenge. It's a great talent for Heroics and PvP but doesn't have a use in raiding. Get Imp Defensive stance. It helps. A lot.
I haven't been sold on the new block value Meta gem. I still think 18 stamina is too nice to give up. I'm sure there is a thread around here that does the math and tell us what's better for a Main Tank to get, so I'd find that and make your own decision.
Belly up to 12 Arcane dust and get the 12 Stamina enchant to your boots. It's cheap and it's 2 more stamina! Or, get Boar's Speed.
The new badge ring is nice, and can replace your old one. Otherwise, get the trashdrop one in TK or once you're in SSC get Morogrim's ring.
Definitely get the new Badge belt followed by the bracers of ancient phalanx as indicated by Veneretio. They are good EH upgrades and great threat pieces.
My biggest question is why you matched every socket bonus? The one for Crimson Belt of the Indominable is a pretty sad bonus so you might as well just stick 2 +12 stams in there. Likewise the unwavering legguards are stam machines, but to each their own I suppose.
Drop Improved Revenge
and if you can spare it drop Improved Taunt... in raids most things aren't tauntable.
DEFINITELY MAX imp sunder. With it helping your devastate rage as well, its awesome. If you feel you take a lot of spell Damage then go ahead and go 3/3 imp defensive stance but I've never been a huge fan of it except against bosses like Hydross and Kael. I'd personally leave it out and go for better mitigation talents such as 2/5 improved Demoralizing shout. Or get imp heroic strike (take a WWS Log of your tanking one of these raids, your HS will be a pretty big chunk of your damage/threat, the cheaper it is the more you can throw em out).
Well your trinkets look to be in order. I also recommend the vengeance card for the nice stamina and the occassional holy damage can help give your TPS a small boost from time to time.
With regards to your spec you have the right idea but drop imp revenge and imp taunt as neither of these will greatly benefit you in the higher level 25 mans.
As for rings I have not had a good chance to look over the new badge rewards yet (Our server only got them yesterday) but you need the trash drop ring in TK it's incredible and the ring from morogrim is very nice something worth aiming for.
If you get lucky on the lurker below in SSC you can get a great tank mace with expertise which will send your TPS skyrocketing (expertise = god).
As for gems I would advise ditching the def gems if you can hit the cap without them and replace with stamina ones to increase your hp. Once you can get some of the T5 stuff I would recommend gearing with it ASAP you can get some easy T5 shoulders from Void Reaver and although leo is abit tricky the gloves are really nice.
It looks like your going heavily for badge/rep gear which is a nice way to gear up but I noticed the lack of T5 level raid equipment and judging from your gear you are definately ready to tackle SSC/TK and you should do ASAP.
All in all your doing well just sort that spec out as it wont do you any favours later on and you can gain some more HP by picking out your gems and enchants carefully
Ditch the dodge gem on the legs along with the stam/def unless your struggling to hit the cap. Ditch the shield and replace it with the one from gruuls lair even better the one from zul'aman it's sweet as hell and you will notice a significant improvement.
Some people prefer good avoidance but to be honest you should be concentrating on HP for now as it can be a pain when you take no hits for a good 5-10 seconds and you become rage starved which screws up your whole rotation.
I agree with everything Kaze says (here and in pretty much every thread I've seen him post-he knows his sh*t).
I disagree with Imp Taunt though. I think in Hyjal trash and a few cases in BT it really really helps keeping people alive. if it's a matter of giving up a damage mitigation talent, then by all means lose it, but if it's imp taunt or imp revenge I think the choice is easy.