Vader’s redemption starts on ANH when he senses Obi-Wan. Something changes, and he adopts a more restrained fighting style after that point. But before that, he’s quite violent, even on ANH. So the RO scene is perfectly in character I think - we are seeing the prequel Vader.
I don’t see how sensing Obi-Wan, a man he hates, would cause him to go soft or question himself.