My OP was badly written, I don’t see Vader as a joke so much as I was trying to say the DS crew do. Otherwise why would they insult him like that?
I do think Vader probably was messed up mentally, dude spends a lot of time staring into warp speed streaks.
Plus failing onto the banks of a lava river doesn’t do much for one’s complexion.
I never had any problem with fitting Vader’s appearance into the timeline.
Even ignoring possible Dark Side effects on health or appearance, we have several indicators in the movie to let us know that Vader is not a healthy individual, including the “more machine now than man” line from Kenobi. I’ve seen how drug use or serious illness can age a person artificially, and the little we see of Vader’s face is so scarred that it’s hard to get a good sense of age anyway.
Also… the ghost of Anakin in the original ROTJ looked nothing like 65 years old. He fit nicely in a 40-50 year age range. (The ret-conned version now shows the teenaged Anakin from the prequels, of course, so that comparison isn’t so helpful anymore.)