I had issues with Sarevok myself.

Viconia not so much.

First things first, Sarevok always struck me as looking more Kurd-ish than just straight up Michael Clarke Duncan. And no Kevin Richardson is GREATLY disappointing on his front.

As for his role in the story, the only way I could make it make sense is if the original Bhaalspawn took away his will(which is an option in the original ToB) and then when he was gone, Sarevok with no will of his own defaulted to being a mindless slave of his heritage.

Viconia was underwhelming, but otherwise she was fine.

You just have to assume for both of these, neither were redeemed even though that was an option in the original games.

I also learned that after 20 years, Viconia did not in fact gain a new streak of blonde hair in BG2. Imagine my surprise realizing she's actually wearing a hood. I feel especially dumb, because that directly falls in line with how she's introduced in BG2 lol