You've got alot of talents that are not usefull for tanking such as Gargoyle, Rune Tap, Butchery, Master of Ghouls and Death Grip. I personally favor Unholy for tanking as it is a very high threat build and the best for AoE tanking.
I would suggest the following:
Talent Calculator - World of Warcraft
As for your mitigation, it is something that will only come with gear. Every single piece of your current gear can be replaced so get to running those heroics and 10 mans. Run the hell out of Heroic VH for Bolstered Legplates - Item - World of Warcraft and heroic AN for Essence of Gossamer - Item - World of Warcraft and Ancient Aligned Girdle - Item - World of Warcraft. That will get you headed in the right direction.