Progression: Guild is on farm status with all 10-mans with the exception of Ulduar where we're 8/14. We have recently branched to 25-man Naxx and are making plans in the next several weeks to take a shot at 25-man Ulduar.
Gear: My gear is everything you could expect from 10-mans, heroics and badges.
Question: Basically I am trying to figure out the best combination of gear that I can use to be the best all-around tank. I have a large collection of gear and I am trying to figure out which pieces I should wear to find the right balance in the battle of HP vs. Armor vs. Defense vs. Dodge vs. Parry.
Currently: I try to wear the gear that gives me the most HP while also staying above the 540 defense minimum, this setup can be found in the armory link above. Unfortunately going with this method I continually lack the needed points to maintain 540 defense so I am having to use Defense elixirs to meet the 540 requirement.
Slot By Slot Breakdown: (note, I will only list slots that I have more than one tank item for)
As mentioned earlier, I am trying to simply figure out the best combination of gear to wear while staying as close as possible to 540 defense while also maintaining the other critical tanking skills and HP... and I'd love to give up my reliance on Defense elixirs if possible.
A few things. Get the proper helm enchant from Argent Crusadae - 37stam/20def - it's a lot better than a LW patch. Use the stam/armor meta gem over the def/sbv, much more bang for your boss tanking buck.
Get the defense enchant to your chest piece, and to your cloak if you don't already. That should sort out your defense elixir issue, and you can use a HP flask instead, or a better elixir combo (hp/exp maybe).
For boss tanking, Ulduar tanking, etc.. you'll get more mileage from avoidance/threat pieces than block pieces.