Nathan was in France doing publicity for the movie. He had initially been signed up to attend Dragon*Con, but had to cancel. I've heard that he's very chatty in panels, so I suspect that we may have heard more from the others because he wasn't there. It's funny, Adam became the de facto leader in Nathan's absence. They do have a chain of command thing kicking. lol

You're right about Joss. Several of them said that you could see how invested he was in the characters and that made you want to go that much deeper with them. They showed a clip from the movie and it does look really good. I'm looking forward to the premiere. :)