First off, please, don't pass on tanking gear just because it's blue or dropped in a normal or heroic. Just because it's not iLevel 232+ doesn't mean it's not good. You should be collecting and using upgrades as they drop, even if they won't immediately put you at 35K health. Please remember also that a lot of people ran these instances and heroics back when Wrath first released with 22k or so health: despite what speed obsessed or hyper geared players will tell you, it is indeed possible to tank all the original Wrath heroics in blues.
Take the Nerubian Shield Ring, for example. If this drops and you don't have better, roll need on it. Don't worry that people will lose their shard, don't let people give you grief on gear not being up to some ridiculous standard, just take the ring. It has armor, defense and stamina. If you're there as DPS but you want to build a tank set? Roll need if you don't have better. Just ignore people who give you grief over it, clearly they don't understand how important every possible upgrade is while building a tanking set.