I've just started running Heroics the past few days, and Im kind of stumbling my way through Gear/Talents. I was wondering if you guys could give me some pointers on where to focus my time and what I need to change.
Your spec is good, for where you're at.When you get into tanking raids, you'll want to switch 2 points out of Cruelty and into Imp Disciplines. I'd change your Glyph of Sunder Armor to Glyph of Devastate, which is a higher threat glyph. As you move into raids, I'd definitely pick up Glyph of Shield Wall as well.
In terms of gear, you are way over the defense minimum. While that's not a bad thing in itself (it still increases your avoidance and block chance), you would get more out of replacing defense gems with stamina gems, only making sure to stay above 540 defense.
Aside from that, keep plugging away at heroics and the normal versions of the ICC 5 mans, as well as ToC 5 and picking up any tanking epics that fall your way. Snagging The Black Heart out of ToC 5 would be very good for you.