I've never cared for Viconia or Sarevok much in the original games, but OP's analysis seems convincing to me. I never knew about Viconia's story in the original games. It brings a tear to my eye just reading about it here.

I always play goodie two-shoes characters, but I can still have some manner of respect even for the most ruthless villains, so long as they're written well. I'm not sure I'd consider any of the villains in BG3 to be written particularly well. Part of the problem may be that there are too many different villains, so we don't really get to know any of them too well. Part of it may be something else...

For me, the best example of an awesome villain in the series is Jon Irenicus. In a way, he's a ruthless lunatic. An existential threat who needs to be stopped at all cost and deserves NO mercy. In a word, contemptible. This sets the scene for an epic villain, but we're not quite there yet. The thing is, despite how despicable he is, you just have to marvel at him. The sheer power, ambition, pragmatism, charisma, and twisted sense of revenge against the whole world inspire fear and awe. He personally torments you and your loved ones to no end, makes you chase him through the entire game, and treats you as a mere tool and a nuisance the whole way through. (By the way, his voice acting was magnificent and is probably the main thing that made him so charismatic.) Hearing about how he tried to cling on to the last remaining memory of something beautiful, Ellesime's love, but had it slip away piece by piece, leaving nothing but a hate-filled maniac with a pitch-black soul... It almost makes me pity him, in spite of everything he did, and in spite of the fact that this is all caused by his own egomaniac nature and childish entitlement. That's just how much charisma he exudes. He's so utterly convinced in his own entitlement, that it almost convinces you as well.

In a way I'm sad there aren't more references to Irenicus in BG3, but maybe it's for the best, since the writing may have had gone wrong for him as well. Wouldn't want him to get the same treatment as Viconia.

The closest we got to a truly respectable villain in BG3 may be Ketheric Thorm. We get quite some exposition to his tragic family history and learn about his fall from grace. But his final moments still lacked a certain punch for me.

Maybe there was a general problem with the writing of evil characters in the game. Some of the good characters are truly awe-inspiring in how well they embody righteousness, chief among them Aylin, who may be my favorite BG3 character even though I'm more of a Neutral Good player and she's a Lawful Good paladin cliche. When it comes to the villains, I think my main issue is their lack of conviction and self-righteousness. I think this is an important aspect of a good villain. No matter how twisted they are, there has to be some deep conviction that they're rightful in doing what they do. Yet look at the big bad three. Orin is just a brainless sadistic maniac. Gortash is a tired stereotype of an evil scheming politician who literally knows that he's evil and doesn't care. Ketheric shows some self-awareness, but it feels like he's given up on the inside already when you corner him. You can pretty much convince him to give up right then and there (even if it still spawns the Apostle) which ultimately makes him come across as weak in personality.

Anyhow, this is a lot of harsh critique for what's an amazing game overall. The main characters really carry it, I guess, so let's hope that WotC will treat them well. I'm sure there were a lot of zealous fans who took the criticism way too far and made it personal, which is sadly how these things often go, but I hope the writing team can still take away some constructive criticism from the issues raised by OP and others.

https://bg3.wiki/