I'm sorry, but any sort of mitigation diffirences havent been true since 2.1. Damage taken is virtually identical, but Warrior has so many more tools and damage dealing/enmity grabbing things available to it.

With 25% more HP and 20% more healing, combined with Inner Beast's 13% overal reduction (has 6s -20% on what is pretty much a 9 second recast) that MORE than equals Shield Oath. I say equals since i dont want to step on anyone's toes, but between you and me it blows Shield Oath completely out of the water. Math-wise it means that warriors get hit for 87%, while paladins get hit for 80%, so you're exchanging 7% more damage taken for 25% more HP and 20% more healing. That's rediculous.

The thing that happens is that they see a Warrior with 7000 HP and a Paladin with 7000 HP, and they see the warrior is doing worse.
(pro-tip: That would be i70 gear on the Warrior opposed to i90 on a Paladin to hit that HP)

Warrior really is rediculously more powerful than a Paladin at equal gear levels.