I liked their ending, and it was nice to not have a lot of the stupider stuff from Frank Herbert's stuff muddle up their books. The Golden Path was just not a good idea, having it be completely pointless is a good thing in my opinion. You could take it to show how people who "see the future" are, in the end, not only not perfect, but can even be very, very wrong. Then again, you could also say that, while Leto was wrong in his interpretation of the future, his actions did eventually lead to Duncan "evolving" and doing what he did in the end, so his "golden path" did save humanity, just not the way he thought it would.
I do have to say, while I still think Dune and Dune Messiah are the best books in the series, I like BH/KJA's writing style more than Frank Herbert's style. There is more story, and I don't have to spend time reading pages of stuff that doesn't move the plot or characters forward at all and seems to just be there for page count, like basically every word of Leto at Jacarutu. There was seriously probably only enough plot to fill one or two pages, but its filled out with a bunch of vision stuff that I really couldn't care less about and was just annoying to read. To me its the one big flaw in Frank Herbert's Dune books, how he liked to just shut down the actual plot to go on tangents with the characters talking about visions/philosophy that went nowhere and were almost never explained well. I don't care if Leto sees a future where he's sleeping with a random fremen woman or what his justification is for becoming the stupidest looking tyrant in sci fi, just get to him escaping and actually becoming the worm, please. Jessica/Farad'n's talks were also half gibberish.
I do like CoD, even if it doesn't seem like it. But, when it gets off course with the plot, it really degenerates in a way Dune and Messiah never did. You could probably cut 20-40 pages of stuff from CoD and improve it a lot. Cut down the Jacarutu stuff (actually, you could probably cut down a lot of Leto's stuff from the time he "died" to the time he returned, it had important stuff but it also had a lot of pointless stuff that isn't essential), cut all of the philosophy stuff between Jessica and farad'n (just leave a bit about his training because besides that most of their talks are the most gibberish of anything in the book, especially his "graduation"), and some of The Preacher's speechs (although to be fair his stuff was somewhat straightforward, or atleast not boring) and I think the book would work better.