It's common knowledge that Rogue One: A Star Wars Story went through extensive reshoots. It's also well known that the end of the film saw the most changes. However, we had no idea that one of the most memorable scenes in the film came so late. As it turns out, according to John Gilroy, one of Rogue One's editors, the Darth Vader sequence at the tail end of the film that has him tearing through Rebel soldiers wasn't in the original cut.
What was added --- and it was a fantastic add --- was the Vader action scene, with him boarding the ship and dispatching all those rebel soldiers. That was something conceptualized a little later. ... It was a really great punch in the arm and something I think fans wanted to see.
What made up the reshoots for Rogue One: A Star Wars Story has been one of the major questions that fans have had since the film came out. The fact that the reshoots were so significant had fans worried that Lucasfilm wasn't sure how to make the movie work. While the end result has been viewed positively by most, exactly what was added or changed wasn't entirely clear. However, Editor John Gilroy tells Yahoo Movies that in the original cut there was no second scene with Darth Vader, or at least if there was, it didn't include him violently killing lots of rebels.
As much as we'd love to see the original version of Rogue One: A Star Wars Story, if only to know what the original plan for the movie was, it feels like, with this one piece of information, we can say that the reshoots were probably the right move. Watching Darth Vader do his worst in that scene adds so much, not simply to the movie, but to the trilogy as a whole. It portrays Darth Vader as a terrifying force of nature in a way that even the original trilogy just doesn't. It ups the tension at the tail end of the film one last time just to get to the audience. We all know the Rebels are going to escape, but watching Vader's wrath, we can't figure out how exactly they're going to do that.
It's almost impossible to imagine Rogue One without that final appearance by Darth Vader. It's seeing both Darth Vader and Princess Leia at the end that sets up the opening of the original Star Wars. Not having them both, and not having the tension caused by Vader's actions, would have ended the film with a very different tone.
Reshoots always cause concern because it tends to imply a lack of confidence in the finished product. However, in this case, it seems Rogue One: A Star Wars Story just needed a bit more time to figure out what it needed.