Regeneration/- is very, very overpowered. Seriously. It means that you cannot be killed at all without a wish or a miracle. Plus, you know, regeneration. Perhaps make it fast healing instead...

Other than that, the class looks pretty good. Heroic Halo should allow a save to negate the effects, and bountiful mercy is ridiculous. Changing it to making one strike doing double damage while striking a foe below half health fits more with the flavor, while being less... OP. Double damage on a full attack = decimate. Again, this class looks pretty good overall. Just change a few things at it should be fine, IMO.