I wouldnt use your build and ill explain some talents that you got:
1) 2H Spec - its so good for threat, but isnt so relevant
2) Unholy Command - usually you dont need to use Death Grip 2 times in same combat. You have Dark Command to taunt target either.
3) Corpse Explosion - i dont think that this be good talent for tank, i would preffer to use this talent in arena, avoiding rez. =P
4) Blood Cake Blood - its very good talent, but i think that this is better for DPS.
5) Summon Gargoyle - its for single target, but Unholy Tanks are better with AoE, then i'd try get talents to increase this feature.
6) Unholy Aura - isnt so relevant.
7) Wandering Plague - Tank doesnt have high crit, then this talent wont proc often.
I would use this build: Talent Calculator - World of Warcraft
These are benefits from by build:
1) Bladed Armor - increase a lot of Atck Power = increase base damage.
2) Rune Tap - Self Healing.
3) Epidemic - increase duration your diseases, allowing to use another skills.
4) Ravenous Dead - increase Strenght = increase Atck Power = increase base damage.
5) Virulence - +1% Spell Hit
6) Full Desecration - +5% damage in that area.