Sounded like 1977 vintage Vader to me. People sometimes forget the way he sounded before they changed it for the SE.
The ‘mechanization’ of his voice in '77 was stronger than it was in the later films.
I will say that applying a slight bass boost to the JEJ lines brings his voice much more in line with ESB/ROTJ. I did this to the Vader/Emperor speech from season 2 and it feels like it was taken straight out of ESB.
Something to consider for anyone doing fan edits of this series.