Regen is a great defensive passive, but I believe it needs a small tweak: make the damage resistance constant. It gets rather hard to tank when your 30% resistance suddenly becomes a 5% resistance because of a strong attack.
I agree, Defiance needs something to make it stand out. Currently, it takes the worst of Invulnerability and Regeneration: it only adds resistance, and takes some time to build up to full power. Before the On Alert update its big advantage was when it was combined with Enrage. Now that Enrage is a form, Defiance has become…