There are attacks that are not mittigated at all so a 26k tank vs a 31k tank like will behave differently.
The only way that a 31k tank behaves differently compared to a 26k tank is that the 31k tank 31k tank gives their healers a couple extra seconds over the already impressive 15-20 second reaction windows that 26k hp provides. All you're doing by stacking that extra 5k hp instead of 5% absorb is, in those scant situations where you're dealing with large amounts of unmitigatable damage (re: Kephess the Undying, T&Z, twin tanks), providing your healers with a redundantly larger window. If the existing 15 seconds that you can manage with 25k hp isn't enough to keep you alive, it's because your healers are bad.
Endurance does nothing to make it easier to heal you. All it does is make it so that bad healers seem less bad because they can stand around doing nothing for 10 seconds before they realize they need to actually toss some love your way.