The best general mitigation talent is parry in the arm tree. It pretty much beat anything from the prot tree excep maybe improved block. Not taking it while trying to have a protection built seem really stupid to me.
I'm thinking something like this would be pretty damn sweet for a PvP prot kinda build/equip.
Sadly, the equipment requirements are pretty much pie in the sky and the spec itself would be about as rubbish for tanking as a 31 Prot spec could be. And on top of that, I don't think it would be as much use as just running out with a Might of Menethil and smashing people around the face and neck until they had to go for a lie down.
Of course that doesn't have defiance, pretty much the main reason to go prot, you could always substitute points from toughness/iron will/imp sunder to put in defiance. A warrior specced like this would be great to have in wsg/ab. They could keep a target stunned for a bit, shield bash a mage that's nuking/healer that's healing, and they could take one hell of a beating from a melee opponent.