I think that Vader going all the way to Tattooine only to find an empty palace would make him seem even weaker than he does in ROTJ.

Really, there only needs to be one scene:
Fett: "Skywalker is here. I can deliver him, but it may be in pieces."
Vader: "I want him alive, bounty hunter."
Fett: “As you wish.”

Then Fett’s actions during the sail barge scene would make more sense. He originally tries to hold him at gunpoint, and when that fails he tries to wrap him in cords, then when that still doesn’t work and realizing that Luke is too powerful for him to handle he goes for the kill.