I think that in terms of story and logic, making Halsin fit as a companion isn't a crazy ask (minthara is more of a problem there in my opinion). The reason I say including him was a mistake is that Larian has proved that they weren't capable of doing it. They either didn't have the time or the skill to odo it in a way that worked and was satisfying. Which we can see by the fact that they did not manage to do that. In theory including Halsin is totaly fine, he's got stuff goingi for him that plenty of folks seemed to resonate with. It was a mistake because Larian themselves overreached in trying to include him, so they shouldn't have tried in the first place. Maybe another studio could have done it and it would have worked perfectly, but not Larian. They couldn't get it right the first time and now they're constantly trying to fix everything that the inclusion broke, including the chararcters themselves. Assuming they even agree that the characters are broken, which I'm not convinced of.

Ultimately I'm of the opinion that Larian do individual things pretty well, but they make bad decisions when it comes to tying it all together and when it comes to knowing what to include or what to cut. The whole is lesser than the sum of its parts.