Actually, reread the PHB fluff with Clerics. They don't have to be ordained. The reason Clerics can be 'of a cause' is to allow faiths that don't have Deities, such as that presented in Al-Qadim, in my view.
Paladins are certainly not definition B secular (i.e. in the sense of uninterested in religion), but that is not really the issue. Paladins receive divine protection, aid and spells. The source of that power is Divine (in the D&D sense of Arcane and Divine). It does not follow that Paladins receive that power from a Deity or group of Deities, unless that is the only way such power can be granted in a given campaign world. Divinities (in D&D) acquire Divine power themselves, they are not actually the font of divine power. There are (for instance) limits to what they can do.