Can you show me the source of your "math" that says "Astarion == evil", etc? Because 5e doesn't have strict alignment anymore.
I don't think you can honestly appraise Astarion and not have it be clear that he falls into the evil companion camp. He's petty, cruel, mean-spirited, sadistic. Is he also sympathetic? I think so. Is it going to be possible that he'll have the option of redemption? I think that as well. But as it stands, if left to his own devices he's gonna be evil. He's the most straight-forwardly evil companion we have in terms of behaviour. I suspect a lot of players who don't know about Shar would assume Shadowheart was pretty much good.
And Karlach and Halsin I'm sorry but I cannot count because given Larian's track record thus far of NOT being adequately forthcoming with information about the game, I have zero reason to believe or expect we will have anything more than 7-8 total companions in the end.
I am also going to point out that I don't believe there has even been a hint that Halsin is going to be a companion (I honestly wouldn't want him to be either, he's an Archdruid, that sounds like someone far above us in terms of level, he makes sense as a mentor and guide, not someone equal to us) it's just a thing people want. Karlach at least has datamined stuff and a mention in the related MtG set, whatever that's worth.
