Angelic Divine Bond

[d'Eon]

So I was looking over the options from Healer's Handbook, and I saw the alternate divine bonds for paladins. Checking the additional resources, I see that Agathion and Archon are legal, but Angelic is not. Why? Is it just that much better than casting communal protection from evil?

[GreyYeti]

The bonus it provides scales, so it is a +3 bonus on level 5 (already better than protection from evil), a +4 on level 8, a +5 on level 11 up to a maximum of +8 at level 20.