You need to get uncrittable. One of the things you can do is put 30stam +15 resil enchant on your shoulders. That will leave you 8 defense points away from uncrittable, and you'll be almost uncrittable in heroics (with the resil encahnt it's 531 uncrittable in heroics, 536 uncrittable for raids).
Trinkets: Easiest ones to get:
The Black Heart - drops off of TOC5 normal, so it's farmable and is VERY VERY good.
Essence of Gossimar - drops off of Anub'Arak in heroic Azul'Nerub
Glyph of Indominability - 50 badges of Triumph.
Also: you may want to pick up some 20 def gems (at LEAST 16 def) to try and get uncrittable, then start stacking stam after that, but make sure you keep your meta gem active. Also: get the 37stam+20 defense to helm enchant (revered with the argent crusade). Between that and the shoulder enchant you'd be uncrittable in heroics, and close to uncrittable in raids.
That's where to start at least.