To reiterate on what others have said, you should be fine to start heroics, however that doesn't mean they will be easy. Going with a strong group you can rely on will make things considerably easier. In the meantime though there are a lot of ways you can work to improve outside of heroics as well.
While a lot of your gear is likely to be replaced quickly, you could enchant a fair amount of it at least with old Wrath enchants. Chances are your auction house is flooded with scrolls yet from all the enchanters who were leveling up, lowering the prices a fair bit. Not that enchants will make or break you, but you could probably afford to invest a little bit in that department.
You logged out in PvP gear which doesn't help much since any and all Resilience Rating is wasted in PvE. Work on your faction reputations through dailies and wearing their talbard to get PvE upgrades. There are 333, 346, and 359s you could buy through factions you could gain significant reputation with simply by questing through their respective zones. Your closest to Revered right now is Therazene which will get you a ring upgrade. Technically you could get the Strength DPS ring and reforge one of the secondary stats to be a tanking stat like Dodge and get two Ring upgrades. You could already buy your Honored shoulder enchant from them. Guardians of Hyjal has a 333 tanking neck at Honored (you can get all the way into Revered simply by questing through the Hyjal zone which only takes about 3 hours to do the entire zone). You also get a 359 epic tanking cloak from them at Exhalted. The Earthen Ring at Honored (which you already are) you can buy 333 tanking pants to replace your PvP pants. At Revered you get the tanking helm enchant. The Dragonmaw Clan at Revered you get a 346 tanking helm to replace your PvP helm. That one also has sockets so you can get your meta bonus. At exhalted with them you get 359 tanking boots. At Revered with the Ramkahen you get another Strength DPS ring that is a 346 but would be better itemized for tanking than the DPS ring from Therazene. At Exhalted you get a 359 tanking belt.
You gemmed for Crit rating. Why?
You reforged... Haste, Mastery, Expertise, and Crit to get Hit rating. Why?
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.