Heroics, for the most, part aren't particularly tough if you do them right, even with spotty gear, but you sometimes need to blow your cooldowns, and be prepared to do some serious healing. You also should read up on and think up solutions to bosses which require moving around. Just for reference, my guys in mostly epics have to blow every cooldown and heal nonstop through many parts of the bosses in Heroic ToC.

I recommend having your tank played like you'd play a normal character using a different row from the DPS; same with the healer. My right hand moves the mouse and hits healing keys on the numpad while the left hand hits DPS and movement keys with the index/middle/ring finger, and the thumb hits tanking keys across the Z-M row. Most people don't do it my way, but I figure I'd suggest it to you, since the only heroic I don't do now is the occulus.