I have noticed, at least with the two classes I've played so far, Chapter 1 has a villain that you kill at the end (like Grand Moff Tarkin). Then, Chapters 2 and 3 have a villain that is the primary villain for both chapters, like Darth Vader. If you think about it, Grand Moff Tarkin was by far the main villain of ANH, with Darth Vader in a The Dragon role. I would like it if the main villains were at least hinted at in Chapter 1 though.