Dune is a pretty good book and I attribute that to a ruthless editor. After the author died, the son published many of the notes (sort of the way JRR Tolkien's son did) and one of the books shows several early drafts of the first novel - most of which were stinkers. The notes filled an entire room and he managed to squeeze 15 novels out of them.
Christopher Tolkien was a lot more respectful of his father's legacy than Brian Herbert. However, I think of Barry Humphreys saying that "if you want roses, you need a lot of manure". Even the best writers produce dreck.