Aye pyr0mancer's right thats probably the reason why the civs are all mostly 1 religion. I often have the same thing, only once I had it where The Whole World was Ashen Veil and poor little me was the only good guy. Now that was a slash and burn game. IMHO the devs should make it so the civs have affinity for a certain religion so you dont have people like tebryn and sheela being RoK or FoL, they should only be allowed to have Ashen Veil or maybe OO. Vice Versa too
I wanted to suggest the same. In my latest game all 3 good civs converted to AV because there wasn't any other religion available, it makes no sense. I agree that there should be some weight modifiers that will keep civilizations from adopting opposite (lore wise) religions at least for some time.