"because having two characters put to sleep/incapacitated in a party of six is a relatively minor annoyance, having it in a party of fours can mean being forced to a reload" That is a very good point!
High level characters are much more complex to manage, no doubt, and after a certain point I just do not enjoy that, so I under-utilized the rest of the party in BG II. I don't have a multi-tasking brain, I guess. The Neverwinter Nights single campaign really tried to let you focus on just your PC, and I liked that aspect of it, but it felt really lonely because you could have only one other NPC join at a time. I don't have BG III yet, how is the party AI? As I said before, maybe the turn-based system makes this less of an issue, I just don't know.