I think you hit upon something interesting here. It seems safe to say that Ascencion is *intended* to be Astarion's evil outcome, the way that being loyal to Vlaakith is Lae'zel's and becoming a dark justiciar is Shadowheart's. It could be a thing where the writer's felt that this path (which involves participating in a literally hellish ritual) was self-evidently evil enough that they forgot to show the fullness of why. Personally I think his full going over into evil is also obvious based on who he was and wanted to be before, given how he basically says at multiple points that he thinks having power gives you the right to abuse it, but that's just me. It can easily be argued that the game broadcasts Astarion's evilness post-ascencion without actually getting opportunities to show it. It's tougher to do that when he's still under the control of the player as part of his party, but he also demonstrated that left to himself he'd be evil anyway so it can depend on the viewer. I think that Wyll suffers the same fate but to a worse degree because there wasn't even any pre-establishment based on his character beforehand. There's a weird vibe around his politician outcome at points as if that's meant to be his evil ending, with the game seeming to assume Wyll's motives are entirely different to what he's shown at any point. Probably in part a consequence of the rewrites.
Not 100% related to the thread, but I feel like I stumbled into Wyll's "evil ending" almost by accident. I chose to have him break his pact with Mizora because a contract with a demon seemed like an objectively evil thing, and unlike Astarion, Wyll obviously cares about being a good person so I thought, sure, have him not be bound to a demon anymore. If breaking the pact had insta-killed his dad, maybe I would have seen it as a bad ending, but all that really happened was Mizora messed with us when we did go to rescue his dad (since we were in the neighborhood anyway, saving the other prisoners), so...how is that the evil ending? I think it speaks a lot to how underdeveloped Wyll's material is.
With regards to the ritual being objectively evil, it speaks to something else that I think about a lot regarding the anti-AA crowd. There seems to be this idea that unless you're deliberately playing an evil playthrough, then any decisions you make in the game reflect your values in real life, and that you should strive to make good and moral decisions. They talk about helping break this cycle of abuse/violence, helping Astarion see the good in himself. But the question I never see asked is, is it good and moral to have Astarion in your camp in the first place? Regardless of your shared problem, is it the good choice to have someone in your camp who's prone to biting people, who approves of slavery and genocide under certain circumstances, who generally loathes any purely heroic figures and acts? Who repeatedly expresses gleeful interest in screwing over the only family he's had for two centuries in order to complete this ritual? Forget the fact that he can ultimately not go through with it; the fact that he seriously wants to would be a sign that you're traveling with a bad guy.
It's just interesting to me that the question is always, "How can I fix Astarion?" and not, "Should I even have Astarion in my camp?"
