Round 1 goes to Vader.
- Yoda's Ataru will not be as effective as Vader's Djem So. Vader's Form V is geared towards parries and defense that instantaneously switches into an even more brutal and powerful offense. Ataru is all-out offense by way of acrobatics. Djem So is not nearly as exhausting. Luke is a non-factor in this round.
Round 2, I'd say, can go to either Yoda or Vader.
- While Vader outclasses both Yoda and Luke in terms of raw power, Vader does not have the same mastery and versatility as Yoda. Luke would once again be of no use in the fight.
Round 3, I'm leaning towards Vader, but Yoda is still capable of taking this round. Only, Vader would win more often than not.
- Vader was always approaching fights by way of the Saber, as was his preference. Yoda was the same. The reason I lean more towards Vader here rather than Yoda is for a few reasons. Firstly, Yoda won't be able to break away from Saber combat quickly enough to do a massive move with the Force. He could do a few small things, such as what Obi-Wan did during his fight against Vader on Mustafar, and use the Force to play around with Vader's prosthetic hand. But, that won't do much. Luke remains a non-factor.