Also, Lord Dave, Rey had zero training with a saber yet was pretty proficient. That backs up what Vindictus is saying about using the Force over being a trained fencer.
She also had zero force training yet mind controlled a storm trooper within minutes of even learning she could.
To me this is just a plothole. Or she's a force prodigy and needs no training. Which to me is stupid.
As for Luke fighting Vader: The first time, Vader wasn't trying to kill him. The second time, it's iffy.
But let's say the Jedi don't do saber training. Let's say it's uncoordinated movements that you do while sensing. Completely untrained. So you know that your opponent is going to swing from above. What do you do? Block would be your instinct, but do you know how to effectively block or even counter attack? The force can tell you what's coming but it can't tell you how to react to it.
This would be the difference of a fist fight between a black belt and a normal, untrained guy with the force. Can he see that kick coming? Sure. And his instinct will be to do something. But the black belt will have a much better chance of anticipating his actions and having a counter attack ready. You can predict his attacks, but how do you defend yourself against them in such a way as to avoid what he anticipates?
Sorry but there is no possible way the Jedi are going to give anyone a weapon and not train them how to use it. It's stupid and a waste. And if they did, the Sith would capitalize on that and say "You know, if we TRAIN this guy to fight with a light saber, he'll kick the butt of any Jedi."
Side note: Vader is in a giant suit and is slow because of it. Hence why his style is a very forceful one rather than agile.
Also:
https://en.wikipedia.org/wiki/Bob_Anderson_%28fencer%29The guy who did the sword fighting as Vader WAS a professional fencer AND he did the choreography. So... yeah.