deepanddark20 said:

I think this is actually a major reason that in the prequels the Jedi talk about a set of "trials" that have to be faced before your Jedi-hood is official. Training alone isn't enough for Jedi status. I think that was put in the prequels to offer the explanation that Return of the Jedi was lacking for why Luke had to confront Vader. Since the Jedi have been disbanded in Luke's time, the official trials that existed in the Old Republic days aren't available to him anymore, so his circumstances have to be used to create a custom set of trials for him.

So what you're saying Yoda's really terrible at making those up. "Yeah, we're done with the training here. So, remember that thing you just did? If you do it another time I'll hand you your Jedi badge. No, the first time didn't count because I said so." ;)

The idea of a final trial is fine in itself. Just have it make some sense.

deepanddark20 said:

when a movie leaves room for the viewer's imagination to fill in certain details that are not fully explained, that doesn't always have to be seen as a flaw (though it sometimes is)

It doesn't work in this case, though. What Yoda is talking about has already happened in the previous movie.

Think about it. The whole reason Yoda's able to have this little speech is because Luke's already done the very thing Yoda tells him to do in the speech he's giving him. It's painfully obvious that the scene is there because the movie needs a climax... somehow, but it just doesn't make sense the way it's written.

And it wasn't even that difficult to fix. The idea with Obi-Wan would've been trivial, to name one example. Cutting the mention about completing Luke's training altogether would've created tons of possibilities for the final sequences with minimal, if any, alterations, to name another. Making Luke's purpose in confronting Vader more vague to the viewer by doing so would've already been a colossal improvement. Hey, look, there's some tension in the climax all of a sudden.