You have many truth in your words/accusations about the characters, and I think, most for "unsatisfied players" one of the biggest problem in the game is the companions and their non diverse, their personality ....etc.etc.etc. (the other is the Character creation and the misses and mistakes in there)
As Lyzrl said
Jaheira & Minsc... they seem like Larian's "safe bets".
and I really like them both as well (also liked in the first 2 games), but the others... Let's just say what I saw/get them from E.A. I'm also not so motivated or interested to go deeper in their personal stories or get to know them more...
The only reason why I also have some interest about Halsin and Karlach is the same reason as yours. And in Shadowheart's case the only thing what is interest me is that which of my theory become correct:
-She is an undercover Selunite agent among the Sharrans
-She is a decendant of some high ranking Selunite priest or Selune's choosen
either way, the „turns” like this for me is forwardly predictable and boring.
I'm in a stand that to "Wait and see the final result" (and hope that Larian finally hear and accept the players oppinion about this).
But in this state (or if it remains in this way) they are really far from the "Memorable Companions" which the other Forgotten Realms games have plenty. (like: Khelgar or Neeshka from NWN2 or nearly any companion from BG 1-2, in ID 1-2 some of the NPC was more interesting than our current companions, and some point even in Demonstone had more "deeper" and "interesting" characters)
