Started running heroics few days ago and in my opionion you should be just fine, although some more avoidance wouldn't hurt. Heroic mechanar is really nice place to go since you gain good amount of badges, great tanking sword and Sha'tar reputation for new shield.
About spec, move those 3 points from Imp. Revenge to Imp. Sunder armor. As for Devastate, I don't think it would do more threat than sunder with your current gear, so that might be wasted point.
I've never been a fan of Imp. Revenge. It *can* save your ass from time to time, but it also leads to stuns, which leads to less mobility, which leads to spikier rage generation. Myself, I'd pull the 3 points from Tactical Mastery and the 3 points from Imp. Revenge, and put the rest into Imp. Bloodrage, Imp. Sunder, and Imp. Heroic Strike.
Personally, I always go 2/2 Imp Bloodrage, because I find that my opening rhythm is way off if I can't hit Bloodrage and Shield Slam right away. It's pretty silly, and I could just adjust a bit and free up a talent point...but I just can't wean myself off it. *shrug*
Some people swear by Imp. Revenge, but I'm not one.
You shouldn't be stance dancing enough as a prot warrior to need Tactical Mastery, IMO, but it depends somewhat on what you do outside of simply tanking. I grind with SBV gear on, so I don't chance stances much, even while grinding.
Devastate isn't needed for you for tanking, but it's a somewhat helpful soloing ability, unless you would prot grind with a 2hander.
Your gear is great for heroics. 12k HP/12k Armor is a usual baseline for starting out.
Ok, thanks very much guys, i'll probly change my specc a bit then, after reading a bit more about devestate, solo grinding isn't a problem for me(what with having a mage to grind with ) so like you said maybe i don't really need devestate and TM.