I did write all the companions on NWN2 OC, and Gann and Kaelyn on Mask of the Betrayer. I also did some of the major NPCs and major events as well, including the trial sequence, for example, but I'd have to go back through a fine-tooth-comb to see which ones were actually mine. I admit there may have been instances in a specific area (for some reason, Casavir nags at me) that were done by someone else, so my memory may have missed some elements, and I apologize in advance if that's the case.
In all the instances above, none of the original concepts were mine. It doesn't matter, since execution is the thing, and that's what a writer's supposed to excel at. Your job is to take someone who dresses up as a bat and fights crime and make that shitty (imo) concept work. A more challenging one might be if one of his foes identifies with penguins, but hey, Arkham City made it work, imo (the Penguin's intro and museum collection I thought was great).
Yes, NWN2 OC had a lot of companions, and I do feel I could have done a better job with all of them from minor details to major elements (for example, Grobnar suffered the same problem as Oswald Fiddlebender in Icewind Dale - he was written to be hyperactive, but then that got lost on the way to the VO booth, and had I time to go to the studio in both instances, I could have remedied that at once, and I should have found the time to do so). Their lines are excruciatingly long to be spoken at normal speed, although I still liked Oswald's VO delivery, I believe the actor was Jack Roth.
I also didn't feel that the companions were as tied to events in the game as they should be, and I thought with George Ziets' help (as well as most of the designers on Mask), this was a big difference in Mask. I especially liked how the area designers specifically wove the companions into each area, since I felt like their arcs advanced as you advanced through the game and enjoyed Mask's simple non-linearity as well, which I don't think was a resource drain, but Kevin Saunders and George could probably give a better answer.