There's all sorts of various types of teams. And often the penciller isn't what we'd think of as the penciller - they just do the main figures and someone else comes in and does the backgrounds. And don't forget the influence of the editor - they do quite a bit of story and script work too, I suspect.

And I've been poking around the net looking for breakdowns of assistants, and it turns out - at least in some magazines - only about ten people have weekly stories - the rest run every other week or so, and there's a bunch that go in only once a month, so not everyone's on the same schedule, as well. I'm betting that the weekly ones may be more likely to have separate scriptwriters, although I'm just guessing.