See, Dosadi is one of my favorite books. It's not perfect by any means but a concentrate of Herbert tropes with interesting plot lines. Like most Herbert it's very much for a young adult / adolescent public (this not being a negative, it's pretty thin on many axes, focused on delivering the tropes in a enthusiastic way). The other Herbert 'destination, jesus' book cycle is harder to swallow though.
I remember enjoying reading it and finding the worldbuilding really interesting and the drama kept me reading. But I am a sucker for Frank Herbert so maybe I missed the flaws.
As I said: it is/feels like a sketch. The prose (often) reads like notes which should be rewritten, and filled with depth, and life. Also the story is bad, there is too much "deus ex machina". Also no characters one can relate to. Sounds like you read a totally different book than me :P.
If I had read it and the Dune without knowing their authors, I could not have told them they were written by the same person. Especially not that it was written after the Dune, where he has proved he can write well.