I agree with this. You need a good producer (who understands the artistic process) to help the director see the wood for the trees when they are too close to the film. Example: Robert Evans. The Godfather and The Godfather Part II were both a mess when Coppola originally submitted them (the first Godfather was a mere two hours, believe it or not - he'd cut loads of vital material). Evans took the films out of Coppola's hands and recut them into the versions we have today. Thank God for Robert Evans.

The same principle applies with authors/editors.