I've been reading Tankspot for a while and it's got some fantastic info on. I have recently started tanking Heroics but the group is really struggling. First of all I want to check if I am the problem. Am I geared for heroics and is there anything else I can do to more adequately prepare for heroics?
Gear wise you are ready although only barely. With out a good healer and good dps you will struggle. What your gear is missing is enchants. The argent crusade one for your helm, gem slot for your belt and so forth. Enchants alone could give you 2K health which is what you're mostly lacking. They can easily suck 1000g out of your pocket but it will bumb your odds up considerably.
Also if you really struggle, use CC. Removing even one mob from the fight makes things a lot easier if you're getting eaten alive.