Nonhuman Deities

While I like some of the "classic" nonhuman deities (meaning those in AD&D Deities & Demigods and in Roger Moore's Dragon articles), their existence raises some questions for the world, some of which I have been thinking about as I consider them as part of my detour into the religions of the Flanaess in my Greyhawk series. 

First of all, the suggest nonhumans are monocultural or at least were monocultural at some point in the relatively recent past because all of them have the same gods, or their gods are very activist and keep their worshippers on the right path by constant intervention. Admittedly, this might not be that much of a problem given we're discussing a fantasy world where the gods (at default) are demonstrably real.

The other problem is that how these deities relate to the human deities isn't clear. In Greyhawk, though the human deities have various cultural origins, many are now worshipped by people of multiple ethnicities and cultures. While neither the Folio nor the boxed set goes into this sort of detail, I would assume that this means their mythologies are likewise intermingled. Where does this leave the nonhuman deities that aren't even mentioned in those works?

One solution to this problem (and one I'm sure I'll employ it to a degree if I write on the topic) is to assume a degree of interpretatio humana so that the nonhuman deities are seen as the elvish or dwarvish names or aspects of gods the various human cultures are already familiar with. Another would be the demonization of the deities of groups with whom hostilities exist, so that orcish or trollish gods might be seen as known demons/devils, or simply as yet another of those legions.

The other side of this would be new humans cults emerging that would incorporate nonhuman deities, sometimes with new (and perhaps even erroneous) interpretations. How would one have an erroneous interpretation when the gods and clerical magic are real? Well, again, I think it depends on how you believe those things work.