I've gone back to all the books and to Dramatica's manual and seen I've got it all completely wrong.
I still have a few problems with Star Wars though, even if I agree Luke is the Protagonist, MC and Hero.
Leia is the one tasked with delivering the plans to the rebellion.
Obi wan gets the call to adventure when she passes the baton to him via R2D2 when she gets caught.
Luke is merely tasked with helping Obi Wan deliver the plans, and also help Leia - so he's just kind of Obi's helper and jedi apprentice.
Luke then becomes Leia's rescuer, and helper to get the plans away from Darth and to the rebellion. Even the plan to rescue Leia quickly becomes Han's plan, assisted by Luke.
So although Luke mostly plays secondary dramatic functions he's still the protag, as without him all would be lost after Obi gets killed by Darth. And of course, he's the one who actually destroys the Death Star and transforms because of it.
Assuming the above is a fair analyssis, now I need to apply Dramatica to Thelma & Louise, as this is the kind of story my own idea most closely resembles - at least in the method of assigning role functions.