The first thing I noticed is your dodge is very high (parry should be about 2-3% higher than dodge on average) I'd reforge dodge into Mastery first if you can if you can't do dodge into Parry get those values reversed.
Do you have the Baradin's Hold mastery trinket? I'd use that instead of Stay of Execution which is pretty lame for prot warriors. The magic number you're looking for is 102.5% avoidance you get 5% miss base. By my math you're currently at 95.86% look at getting your mastery value up as that'll close the gap quickest.
I'm not sure what flasks / elixirs you're running but if you're running a flask I'd recommend picking up an Elixir of Mastery and Prismatic Elixir instead you get 225 Mastery from the Elixir which will definately help and use Lavascale Minestrone which is another 40 Mastery from the food.
These things combined should get you at or close to unhittable. I'm not able to analyze your play style so I can't say if that needs changing but unless there is an ability you anticipating needing to shield block through (crackle on Nefarian) I'd advise using it on cooldown, you have the 4pc t12 so that'll give you an extra 6% parry every time it expires.
I don't know officially where we stand as tanks but in my raid I'm the preferred tank as the healers feel I take less / more consistant damage making me easier to heal.
In terms of threat, always open w/ a charge / shield slam when possible for single target, for AoE charge/heroic leap, rend, thunderclap, shockwave I believe is the correct order. You can usually hit heroic throw as you're charging in for extra threat as well if it's not needed to pull aggro on a ranged mob.