As you say, the Evanuris are implied to be way worse than the normal shades of grey that Bioware use. Why is that? Surely it goes against the way they normally depict things. Why did they have to remove the Dalish belief system so comprehensively, so they have no alternative but to be atheists, unless they want to roll over and accept the religion of their oppressors? I'm only trying to find an alternative to Solas' version because normally we are given a more balanced view of things. The fact is though that the gods that the Dalish revere are not the Evanuris, they are the Creators. They even have a different collective name. The Dalish remember them as guides and teachers of the community. Isn't it conceivably possible that their tradition is about an earlier period before the war that led to their elevation to godhood? There was clearly a period when they were not gods but simply guides and teachers as the Dalish lore suggests. The Dalish do not mimic the gods as they were as tyrants. When in the Dales they did not have slaves. The humans may not have destroyed their main empire but the Tevinter did destroy the elven community in Arlathan Forest and did their best to obliterate any evidence their history and culture. Is it any wonder that I feel sympathy for their situation. Are you telling me that from the beginning the writers wanted us to despise the Dalish and this latest development is their reaction to our failure to respond as they wished?
The way it is headed is that the Evanuris are going to be made responsible for everything, including the Blight. Where is that going to leave any of the elves, let alone the Dalish? Likely forced by the writers to join Solas and then be killed in large numbers.
Mind you, I think they are setting up the dwarves as well for a rubbishing of their traditions because of the reveal about the Titans and the fact that there is evidence of the Shaparate tampering with the records.
Drakon wiped out every religion and every cult to Andraste that did not agree with his own version of the faith. There is a great deal of blood on his hands in the spread of his faith. What we have now is likely not what Andraste intended. There is no guarantee that we even have all her words. Why does no one question this? Why should my Dalish PC or my city elf PC accept a faith that we can patently see to be the creation of Drakon?
Why are the historic aggressors the Avaar, who have repeatedly attacked the lowlanders, been given such a positive depiction of their culture compared with the Dalish? Why couldn't the Dalish gods have been simple spirits like the Avaar? May be my Dalish Inquisitor will adopt the Avaar gods instead? He is after all an honorary member of the Avaar.
I don't know why they Bioware decided to go this direction with the elven religion. As I said, I was not happy about it. But while most things are intended to be grey, Bioware does go pure evil with some characters. A few Tevinter magisters come to mind, so do many of the characters in DA 2.
And yes of course you're right that the Dalish have very specific view of the Creators that is very different from the cruelty of the Evanuris, but the fact that they believe the Creators are gods at all must be based on the height of the Evanuris' corruption. Before that they weren't believed to be gods at all. I honestly think the implication is supposed to be less that the Dalish legends were based on some real period of benevolent rule, but more that the elven religious tradition was shaped by nostalgia for a time before they were enslaved by the Imperium, and so they eventually forgot about the brutality of their own rulers.
I'll say this abut Descent though, I actually thought it improved the credibility of certain dwarven religious beliefs. We always knew the Shaperate's record keeping was meticulous and detailed but also corrupt and politically motivated. That wasn't even a secret in Dragon Age: Origins. The fact that they don't have records of certain things is not a surprise. But I don't think DA had ever really explained what a Stone Sense even was before. Before Descent, I suspected it may well have just been a dwarven superstition. We also don't really get clear answers about exactly what the relationship between the Stone and Titans is. Afterward, Valta seems to have new unexplained powers after connecting with the Titan.
Regarding the Avvar and the Dalish, as I also said, my guess is that (especially since we never really learned as much about them until Jaws of Hakkon) the Avvar don't have a history of being considered noble victims by the fans, so there was no desire to try to "level the playing field" when it comes to fan sympathy. I did notice that even the friendly Dalish you first meet in The Exalted Plains basically even laments how xenophobic his own people are.
That said I don't think the Avvar religion would work for the Dalish and more than any other outsider. The Dalish believed their gods were real beings, not just various generations of spirits manifesting their ideas of them. That might work for the Avvar religion, but I think if that were the case the Dalish religion as it currently exist would still be discredited. Maybe not quite to the same extent as it is now, but still.
Also it's pretty huge oversimplification to just describe Andrastianism merely as the religion of their oppressors. It is also the religion of the prophet who freed them from slavery and the religion of their own founding hero. And as Ameridan and the Canticle of Shartan both show, there was an elven religious tradition of Andrastianism present even in the Dales. Just because the Chantry has tried to erase the memory of that doesn't mean elves or anyone else would be right to do that same.
If it's not under Divine Leliana, then joining the institution of the Chantry itself would be a bad choice, but I can definitely see the appeal of the Cult of the Maker for Dalish who learn more about its forgotten traditions. I actually imagine at least one of my Dalish protagonists would convert to it after learning the truth of the Evanuris.