Maybe prominent isn’t the right word, but everytime he appears, he’s being hugely built up, completely relying on the fact that everyone in the audience knows him. He was blown up to appear more important than he really was.
The first scene in the castle was absolutely insignificant to the plot and Vader hacking through rebels seemed to be below him. In Star Wars, he could have single-handedly boarded the Tantive IV, killed all the soldiers and so on, but he sends stormtroopers to do that, because it wouldn’t be worth his time.