Oh, of course. My question was not about whether gods in their entirety are necessary. I personally really like the idea in Eberron that the Sovereign Host is a pantheon of "deities" for which there is no proof that any of them even exist in any sort of tangible form. People just have their faith and can manipulate magic because of it.
My question was more about whether anything is gained having tangible, interfering evil gods that supercede the tangible, interfering devils and demons? What makes having both layers of evil entities worthwhile? Or does the redundancy reduce either sides importance?
(Of course, on a similar note I suppose I could ask the same question about all the pantheons of the Forgotten Realms themselves, as they seem to be tripping over each other's portfolios from the get-go. I mean why have one god of combat when you can have Torm, Tyr, Tempus, Helm, and Bane all fighting over their worshippers, LOL!)
Why have good gods when there are angels (solars, planetars, devas)? Or lawful gods when there are modrons? Or chaotic gods when there are slaad?
Aside from a difference in power level and origin stories, I think you are getting hung up on the "tangible interfering" bit. Evil is not a synonym for antagonistic. Consider Umbelee. She is evil because of a metaphor - the cruel sea. Many sailors sacrifice to her, not because they like her or approve of her teachings. They sacrifice because they are
afraid of her. And Umberlee is fine with that, and will kill slightly fewer sailors to keep them sacrificing. That's a completely different agenda to a chaotic evil demon, who just wants to kill everyone. Umberlee doesn't want people dead because she needs them alive to fear her. On the whole, gods, irrespective of alignment, are simply part of the background scenery.
As for Auril in
Rime of the Frost Maiden, we simply don't know what her agenda is or what has caused her to go rogue. By standard FR metaphysics there is nothing in it for her to kill her worshipers, and most evil beings (apart from demons sometimes) act rationally to their own advantage.
A Greek inspired campaign, such as Theros is a different thing again. Those gods can be petty and childish irrespective of "good" and "evil" labels, and it's up to mortal heroes to sort out their problems for them.
BTW, the reason FR has gods "tripping over their own portfolios" is it is inclusive. There are gods from many different peoples and cultures and they are all
real. (and Tyr is an immigrant from another universe altogether).