I read somewhere that actually that all the books after DUNE were written because the first was profitable and he would have kept on writing until that changed.
Dune by itself is a complete story. It needs no other books to complete it. The rest of the novels afterwards tend to build off each other. In particulary, you don’t really understand one until you read the next one.
And actually, I would argue that if there is a trilogy, it goes from** Dune Messiah ** to God Emporer, because it really isn’t until **God Emprorer ** that you unstand the constant references to the “Golden Path” in Childern of Dune. Or perhaps just put everything before “Heretics of Dune” in to a single story arc.
My post was a general comment, not a specific response to yours. I was just pointing out that some of Herbert’s ideas now might appear to be cliches because of how many times they’ve been used in the decades since.