Going through this piece from the lens of Dune, several things caught my eye. Firstly, Weber defines a state as having a monopoly over all legitimate violence, but where does that leave the Freeman, for they do have the power in the dessert throughout the history. Between the Leto Atreides' plan to use the freeman's power and the Harkonnens and smugglers acknowledgment that they have little place in the dessert and all but acknowledge the legitimate right of the Freeman to the dessert. The entire Duniverse is a very tight balance with tightly controlled violence. Although, what everyone must realize is that it is the Guild that has a true monopoly over the means of violence as well, as there was no point in having troops an armaments if there is no way to get them to the offending planet.
Secondly, on Webber's point that politics is best run by those who devote there lives to it, and everyone else is just to disinterested, Dune represents a perfect model. Having gone back to the feudal system he speaks to, the Duniverse is run completely by those whose economic wellbeing is set so they have complete time for political maneuverings. I would even place a majority of the Bene Gessirit and the Guild as an institution in this category as they would attempt to subtly alter the politics. The people and most plants seem to be relatively indifferent to politics as it seems their specific duke or leading House was subject to change without too much a notice. But this supposedly should not interest them for they were still under the Emperor. The Freemen seem to be the exception to this rule of common apoliticalness. Within their own governing structure, there are leaders, but they are placed there due to their own skill and through the respect of their people, meaning that the people are actually paying attention to and involved in the political process.