It depends on how one defines "efficient." Yes, the TR was an oligarchy, not the comic-opera dictatorship of lore. Hitler retained ultimate authority, though; don't ever forget that. It is just that as the war became more intense and demanding of his time, he became diverted with that, which allowed others like Bormann and Himmler to horn-in far beyond their proper roles.
However, in some other context, division of powers and competition would be a celebrated advantage. So, the Nazis get slammed because they were a command system (not really true) and they get slammed because they were not a command system, but an oligarchy that valued competition amongst those who held power. In the U.S. we call this gridlock, and it is supposed to be a good thing. It prevents anything from middle-of-the-road reforms from being made and occasional mischief. It's also why we have a thousand companies making widgets and jockeying for market-share.
Actually, a major advantage of the Third Reich over parliamentary democracies, related to but not the same as efficiency, is that applying the military Leadership Principle to politics tended to cut through gridlock and actually get things done, because the only competing interest was the national party. As the saying goes, Mussolini "made the trains run on time." In theory, the Führer decided what was in the national interest, not party politics or litigation. But during the war, Hitler increasingly delegated unwisely to people who would merely cause him less distractions and not the best possible subordinates. He neglected his unique political duties to micromanage the war (which, despite the postwar whining of the generals, may have been the only way it could have been done).
Yes, the TR was a bureaucracy, with all of the red-tape, irrationality and contradictions associated with that--but so are all European states by American standards.
I haven't read Kershaw yet but my impression so far is just more of the same feel-good Democracy-Capitalist apologia. It is really bothersome to the moral elite that the Nazis still have admirers after an unprecedented half-century of propaganda. But, for all the faults of National Socialism, it at least intended great changes. It intended to be reforming and revolutionary and to upset the old order. This makes it an Idea that at least strove to think outside of the box. And the most frightening aspect of it, from a D-C perspective, is that it convinced the majority of Germans and many non-Germans to work and fight for this Leader and his Idea, almost with one voice.
No, I'm not trying to argue that it was pluralistic by any means--war itself is Totalitarian--it is just that no matter how much the Germans disagreed on many things, they agreed on Hitler's core aims. He was the only one dedicated to overthrowing the Versailles encirclement, something that both the Left and Right hated. I'm also not arguing that Hitler did not abandon his more idealistic and progressive social and economic reforms to fight his war, but that doesn't make those goals phony either. And, yes, I know that the NSDAP never won a majority in a popular election--neither did President Dubyah. They did, however, have plurality.