There isn't much in the protection tree that allows a full protection warrior to survive better than a warrior w/ 15 points in there, so what makes other warriors last longer is that they have more +defense gear. At +125 defense, you have 5% more chance to parry, block, and I think dodge, and reduce another's chance to land a critical hit on you by 5%, reducing the burst damage mobs can land on you, which helps a ton.
Extra armor, extra defence, extra resistence to stuns, increased aggro, cheaper sunders. Protection spec rocks.
I'm currently at 436 def, 7k armor and 5k health and busy spamming the mc for more epics.