I think that's part of what makes Modesitt writing work. In a lot of the cases, the protagonist isn't the important part of the book, but rather the specific philosophy, or interesting idea that's the basis for the book is the important part.
In fact, I'm pretty sure on a few occasions he's pretty much done the same story, but with the central argument reversed so what was considered "good" in the one story is the "bad" in the other. Like he's done the argument for pre-emptive action versus waiting for evil to act and which is more ethical. Then a few books later, he's run through why the ethical thing is to wait, even if people die. The characters are just a framework for posing the ideas and running through them in a logical manner.