With 50% Base mitigation and 5000 Base HP.

A Defiance warrior would have : 5000 * 1.25 * 2 = 12500 eHP
A Shield Oath Paladin would have : 5000 * 2 * 1.2 = 12000 eHP

a 1000 Heal would mean ...
20% Heal increase = 1000 * 2 * 1.2 = 2400 eHP
For Paladin = 1000 * 2 * 1.2 = 2400 eHP
25% Heal increase = 1000 * 2 * 1.25 = 2500 eHP