I think the voice acting is pretty darn good, so that's not it (for me personally). I thought a bit more about it and I realized that most banter in BG2 did not originate from any NPCs; it was just background banter, such as the shoppers at wakeen's promenade which sounded off in the distance somewhere. In D:OS however if you are near the NPC it will sound right in your face, which is very disruptive in places such as the Cyseal market where you're surrounded by the chatty lil' buggers.
A better solution might be to only trigger banter if the NPC is far enough away from the player.
