As any of the big authors will tell you, every rule is made to be broken. The problem is---most beginning authors would do well to follow the rules, and they might not get published in the first place if they don't. Once you are established, or if you've written an otherwise outstanding book, or if it just works with your project---you can break about any rules you want.

Like Thomas Edison said, "HE@#, there are no rules, we're trying to accomplish something."

Another thing to remember is that Silver6 is correct as well. Dune does involve both extensive prescience and some telepathy, with the idea that all humans share some kind of collective mind by virtue of their genetic descent thrown in for good measure. Part of the essence of the story is concerned with the idea of something like human omniscience (or at least polyscience)...so it isn't at all surprising that the individual POV of some of the characters, particularly Jessica, Paul, and all the other Bene Gesserit and Mentats blur the lines a bit.

Even if Herbert were to be a stickler for 3PLO (which he is not), there would still be plenty of scenes where a single main character is seeing things from multiple points of view. So some of the appearance of poorly defined POV is actually misleading. Herbert is following the rules better than he seems, but he is concerned more with effects than with rules.