The power of Joan of Arc actually came more from the faith/superstition of her fellow human beings plus the plan of some leading persons to use it for political purposes. As soon as she was no longer of political use, her "power" was gone. And it worked only in a certain environment. People like Joan (or Jesus) today would surely spend some time in mental asylums, or be elected as charismatic fanatics into political positions. BTW it should be quite problematic also for pious people (at least French ...) to assume that God gave Joan the power and then removed it. Why?
In the DnD universe we (even me as DnD newbie, thanks to good explanations in many threads) KNOW that there are plenty of "gods" (of a funny variety ...) and that there is an overawing source of power behind/above/besides them. I still don't get it why a Paladin could not take his power from the source directly, if his/her devotion was strong enough. Wizards and Sorcerers can do it too, or not? The color of the spell, blue or yellow, should be seen as a label made by the end user, and so not constitutive.
