Warrior feels squishier than DRK because its tank stance offers no passive mitigation, however Warrior is probably the overall LEAST squishy tank due to its repulsively vast selection of cooldowns. Rampart and vengeance represent your generic damage reduction mitigation, raw intuition is a long-duration f-you to auto-attacks when used in conjunction with awareness, Thrill of Battle + Convalescence effectively functions at around 20% mitigation, and of course you have inner beast and equilibrium in tank stance for those major "oh crap" moments. On top of this, defiance is fairly mathematically close to 20% passive mitigation, but it's a bit more complicated than that.