As i had mentioned, it was a simple calculation. Even if I was wrong in my calculations, insulting me for it is still totally uncalled for.
Damage reduction is as what it is, damage reduction. Though you can construe it as a HP increase but that would mean it is purely translated as a HP increase (being able to take more raw damage than the HP indicated) and not a damage reduction AND HP increase as that would be stacking them, thus i don't understand how your claim that Shield Oath's 20% damage reduction equates to 20% more HP and 25% greater healing potency applies.
We all know how percentages work, in a drawn out battle, PLDs will have greater survivability due to how percentages stacks and that is what differentiates WARs from PLDs in the essence that PLDs are more suited for battles that are drawn out or battles that requires soaking up massive amounts of damage.