WOTLK Critiques Needed

Alright so here goes, I've been working on getting geared to get back into heroics and preparing to run naxx and etc. I hit 540 def, 20k hp and 20k+ armor, but my question is, I feel a bit squishy at times still. I ran two heroics the other day with a priest healer and did just fine it was Violet Hold and DTK. The next day I attempted a DTK again and got hammered (this time it was a pally healer). Am I doing something wrong? I mean I follow a good 969 style rotation maintain good threat but feel squishy as all hell. I'm still using the Libram of Repentance as well. Could you guys take a look and offer some advice up, maybe some gear I should start going for (currently trying to get my hands on the bolstered leg's).

Here's a link to my armory: http://armorylite.com/us/Demon+Soul/kelstet

Could you guys offer me up some insight and advice I'd appreciate it, I went from feeling rock solid as a tank to hovering over my lay on hands and I hate it. :\

Kel
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Kelstet

Have Tank will Travel.

Your gear is fine to tank heroics. If you're a little worried, just use CC. A little bit here and there is no bad thing, if you're not having mana problems.

For the libram, see Ulushnar's thread in basic training on the Venture Co. Libram of Protection, or get the Naxx-10 equivalent (you should be fine to tank in there).