It could be simply that Vader would not say what he actually says in Rogue One and he also would not say it in that particular manner even. Barring the actual voice (Equalization and modulation)

I think his Lines need to be completely re-written but there is a fat chance of that ever happening. It will fall to a fan edit job most likely to fix his dialogue.

Vader is written much more accurately in that Rebels Cartoon I feel.

https://www.youtube.com/watch?v=Uc_G03kx0A4

If it sounded remotely like that I think it would be fine with it (even this is not quite written right but it obliterates Rogue One Vader)