Bingowings said:
No it proves they have a vital role in ESB that is missing in ROTJ.
Framing the hero's quest, giving it context.
As I said myself, they were indeed vital to Luke's subplot in ESB. But they didn't have some proper role of their own. They were just plot dummies for Luke's subplot.
In ROTJ they weren't plot dummies for Luke's character. They themselves actually had some vital role/mission in the storyline.