I think that Yeats is a rhetorician of genius: I just don't think he ever had a quarrel with himself. That is why the letters are so boring. And when Yeats revises his poems, he succeeds only in making them more sonorous.
Take the lines: "Now that my ladder's gone,/I must lie down where all the ladders start,/In the foul rag-and-bone shop of the heart." What is "foul" doing here? What would it mean to have a "fair" rag-and-bone shop? Pope's line in "The Rape of the Lock" about "the moving toyshop of their heart" is much more painful, but it's true that it doesn't have quite the same throb. We notice these things if we attend closely to the words.
Yeats is like someone who's forever crying, "Oh, I'm the most terrible miser!" and you want to say to him: "No, no, you're just a bit stingy - you never buy a round."