Yeah, I’ve always seen Vader as the Emperor’s enforcer who has no real authority in the imperial military except that given To him by the emperor on a case by case basis depending on his particular mission at the time.
In Star Wars it’s, “hey, go find those plans. Here’s a star destroyer to get the job done with.” And once he had Leia, but no plans, it was, “Oh, go visit Tarkin and see what he can do to help pry the info out of her. Show her we mean business. Blow up her home planet or something.” But Tarkin was still the military leader in command.
By ESB it was, “hey, an unkown force user just blew up our flipping Death Star! FIND HIM!! Take whatever the heck you want. Do whatever you have to. GET him.”
But then by ROTJ he was being reigned back in a bit. Perhaps because of just how far he went in ESB…
I’ve also been rather enjoying how the new marvel comics are reinforcing this concept. The writing and stories have been uneven but the over all impression of Vader’s place in the empire is very much what I just described. But he’s also shown to be a very cunning and powerful Sith who is always walking the tightrope of obeying his master vs pursuing his own agenda, which also fits right in with the Vader we see in the films (i.e. Hunting down Luke like he was told only to invite him to join Vader in overthrowing his old master).
I know some might say that aspect isn’t part of his character in the original film. But I’d argue just because the film’s story doesn’t require Vader to be more than a lackey doesn’t mean he wasn’t also everything else we see later. And I’m talking just in terms of the character in the fictional universe. Not Lucas’ plans or “original vision” or any of that nonsense.