Hi Outlined.
With your tanking gear you shouldn't have any problems in heroics. Sure you could get some more hit, but that would only help you in the threat and interrupt departement.
As long as you pay attention to the mechanics bosses should be cake. Otherwise they can and will oneshot you.
In some dungeouns trash really is more annoying and dangerous than the bosses. If you haven't yet, start marking mobs for CC. Best candidates are caster and healer type mobs. Or if you haven't enough CC, burn those down first and keep interrupting.
If you're doing all these things already, it could be that your healers aren't up for the challenge. They have to know that your health will jump up and down quite a bit and start throwing big spells at you early on is wasted mana. (Try a guild healer once and get him on vent. Let him tell you if you're squishy or not)
Hope this can help you a little bit. Wish you the best and good luck.