All this is EU crap. That line makes Vader seem weak and with no agency in the movie. It’s why Vader kinda sucks in ROTJ compared to ANH/ESB, at least until he brings Luke to the Emperor.
To be fair, it’s not EU, it’s prequel stuff. Ady has said that the prequels have no bearing on his edits though.
Personally, I wouldn’t want to see that line go. One can argue that it weakens Vader, but we already know Vader is powerful. If he’s so afraid of the Emperor, it must mean that the emperor is that much more powerful. Besides, the more Vader seems thoroughly whipped by the emperor, the more impactful it is when he gets the upper hand on him in the end.