Defense cap for raids is 540 defense (689 defense rating). As far as Dodge, Parry, and Block go for Stamina and Armor instead. Effective Health is how most tanks build atm. Not sure how this will turn out in Cata but my guess is EH will still be king.
Expertise cap for dodge is 26, 57 for parry, only in specific fights is this truely important for threat such as Ruby Sanctum HM for parry haste issues. Most ICC tanks run with between 10 and 20ish expertise and they are holding threat on 6-15k dpsers. I personally run with 18 on a warrior, just because thats where it happened to fall. Hit rating cap is 8%, have seen tanks with anywhere from 100-400 hit rating, i try to stay above 200 hit rating personally.
For threat using your abilities correctly far out-weighs hit or expertise.
I knew 540 was the old cap. I assumed it had been raised. I'm not sure what you mean by 540/689.. Mine currently is listed at 565.
It also sounds like I can drop my hit and expertise a bit and use some other gems maybe to pump stamina.
Once I get a new weapon I'll try mongoose.
It seems like the new instances still have multiple mob targets for the tank, I'm using shockwave, TC and slamming (at times cleave). I do think at times things get away from me but most people don't assist even when marked. Anything else I should be doing differently?
Just to explain the whole 540/689 thing. A lvl 80 character gets a base defense of 400 which is raised by getting beat on by mobs. This number is 5 per level and is just a base toon skill, at level 85 it will be 425. So at 80 you have defense of 400, but you need to get it to 540 to be raid crit capped. So you equip defense RATING, and it takes 689 defense rating to increase your defense from 400 to 540. You currently have 814 defense rating which increases your defense by 165, 165 + the 400 base makes your defense 565.
Rotation sounds fine for the most part, but you shouldnt be using slam. Baiscally its shockwave, concussion blow, shield slam, devastate, and heroic strike. For mulitple targets swap out cleave for HS amd hit thunderclap on cooldown. As far as aoe packs any groups over 3 mobs and dpsers are doing nothing but spamming aoe they will peel mobs off you, most of the time its trivial trash and doesnt really matter. If toons are dying from pulling off you they will either learn to slow down the aoe, or continue to pay repair bills. In a raid setting the aoe threat is solidified with a second and/or third tank.
Key thing about threat is as long as you know you are doing the rotation correctly, then you can play with your hit and expertise to your liking. Each tank is different some prefer to stay expertise capped and hit capped while others tend to throw it out the window, its all based on your playstyle and what works in your raid/group setting.
One more note on the defense rating, it is going away in Cata. You will be crit immune via the base defense skill of 400 at lvl 80 or 425 at lvl 85, dont have to gear for it just get beat on while questing.
For your talents i would drop the 4 points out of Cruelty in your fury tree. Move 3 of them to Deep Wounds in the arms tree and 1 into Concussion Blow. I would also look at dumping one of your points in Focused Rage and move it over to Vigilance. Vig is great for threat both on bosses and aoe trash. The loss of Focused Rage is extremely minor due to Warriors almost always being rage capped in raids anyways.
For gear i would look at the 245 crafted chest its easily obtainable with triumph emblems and mining mats. There is a 219 shield i belive in regular HoR which would be an up also. As far as raiding goes you gear would be fine in tanking the first wing of ICC 10, i know on some of our alt runs we have cleared through blood queen with far less geared off-tanks than you. Definitely work through VoA each week and go as dps if you cant find a pug/guild run that will take you as a tank. The t10 pieces are crap compared to the 264 off set frost emblem pieces but they are still an up over what you have now. If you can manage to find a first wing run for yourself in ICC you would be able to upgrade your weapon, neck, chest, shield over what you have now. Oh and for the love of tanking gods get rid of your defense trinket. Either get the 200 ilvl +126 stam one from regular ToC (5man) or get the triumph emblems for the 245 armor one. The defense one now is completely wasted on you atm with how far you are over the def cap.