Your gear looks acceptible for the content your working on (toc10?).
Some minor improvements might be not using the 20 def gems but to fill the sockets you can either do some other mix colours (Orange etc.) which can bump your stamina by some amount (Defene minimum for raids is 540 and your way over it not saying its bad, but if your over its better to start gemming stamina or Stam/Dodge or Stam/parry or Stam/expertise if you have some minor threat issues). and taking the free 3% more block !! from the talent woult be improvement on your current spec imo.
The fel fireball is verry deathly to a equal geared tank on that content i remember the first time i came there we died more then a few times on that encounter because the interupter didnt interupt, People should not compare to tanks above there content level.
Further more you can start farming the new ICC instances (HoR might be hard if you have a bad healer).
but it might also be the simple concept of more out of the fire or having the debuff on you which needs to be healed off.
Keep the treat on you,
There is no "ctrl" on Fluxx his keyboard... Fluxx is always in control.