Arguably, Luke does distract Palpatine from micro managing the battle too closely, and Vader might have had an impact had he been outside in his TIE fighter.
As Vader never says Leia’s name out loud, does he only sense Luke has a sister, but not her actual identity?
Those are good points.
I would also bring up the question whether Luke even believed that rebels could actually defeat the imperial fleet and destroy the Death Star.