Reegar said:

And frankly, I wouldn't be half shocked if Yoda told Luke that to give him extra incentive. It may have had nothing to do with really becoming a Jedi.

What did Luke accomplish? Resisting the dark side? He already did that in ESB when he faced death instead of giving in. Sure, he was pivotal in redeeming his father, but so? Does every apprentice have an evil father he has to redeem before earning the official Jedi merit badge?

YODA: "You must confront Vader. Then a Jedi will you be. Because. . . uhm. . . reasons."

A few extra lines of dialogue or exposition on the Jedi training traditions could have fixed this.

This aspect of ROTJ isn't necessarily what I would call poor writing, but it is lazy. Like most of the film. Aside from the special effects.

Does that remind you of a certain other trilogy?

That line would've made more sense if it was given to Obi-Wan. Vader was his friend, after all (not that you can tell that from watching a certain other trilogy), so it's not entirely irrational for him to try to bring him back. Not ideal, but still much more fitting.

Luke facing Vader because Jedi training stuff doesn't really make much sense to me. He already did face him once and passed the test as you pointed out and if it was a typical Jedi ritual they'd probably have to breed their own Sith in order to have them readily available. Or capture them somehow. It gets kind of funny if you think about it.

I also have issues with the Emperor tempting Luke among tons of other things, but then again this might've been inteded as a pay-off to the Dagobah scene. Except there already kind of was one. Man, the RotJ script was a mess.