Registered: Apr 2008
Location: Bringing forth the apocalypse
And then the fact that LotF Luke was challenged on even footing by Darth Caedus, a being who- while on the same tier as Yoda- did not quite display Yoda's speed, agility, and overall potency. I know A>B>C arguments don't necessarily work, but just for you to note that Luke was challenged by inferior foes in personal combat.
In addition, the whole '20 sabers at once' thing- while insanely impressive- was only accomplished under certain circumstances, and he will have to replicate said circumstances against Yoda. And as Yoda was able to handle fast, effective barrages before- as displayed when he fought Darth Sidious- I'd assume he can give Luke a pretty hard time. Although Luke will probably win.
Comparing Luke Skywalker to another high tier character is so damn hard, anymore. There is no doubt in my mind that he is more powerful than Yoda, but to what degree? Yoda would manhandle most of the written incarnations of Skywalker if we base their abilities on just how they are described; you'd need TUF Luke or late LoTF Luke to curbstomp Yoda. I'm thinking that the lightsaber battle is somewhat close, Yoda's speed is heralded in a time where Jedi are capable of moving faster than the eye can see -- so I'm sure he could keep up with Luke. But Force power > finesse and experience, so he'd lose. I'm thinking, though, that it's not quite a curbstomp.