Nothing stops Germany from reforming into a more moderate posture, although the structures in place would at least continue to push the momentum of the hardliners.
The worst outcome is Hitler living for a long time, or another radical taking the helm. The Church would get Nationally Socialized, the Army gets merged into the Waffen SS, and views on ethnicity are further solidified. The Polish question may be answered through similar means to the Jewish question as well.
Someone like Heydrich, Hans Frank or Erich Koch would probably continue the hard line of the Nazi's ideology; there is little reason that Hitler wouldn't want to back the SS as his favored faction in German politics in such a scenario.
It is possible that moderates can take control--the Armed Forces, The Industrialists--but I would think that whoever replaces Hitler is going to be his appointed successor. If this successor is forced out, there is still the question of the radical/moderate split in German politics. And the real strength of the radical position is that Hitler was vindicated. It is hard to see the next fueher of Germany being a moderate after Hitler.
A moderate will emerge sooner or later, to be sure. But that may be the 1970s-80s when it happens. Germany is going to fall behind the USA technologically (its education system is not going to work) and some kind of slave system for Slavs in the Reich is probably going forward, which will further retard economic growth. Indeed, Nazi Germany achieved little economic growth through its own merits, Ian himself wrote a good essay on that point.
Nazi Germany isn't going to fall like the Soviet Union--what its going to do is withdraw to a homeland, which will probably include Poland, the Baltic States, and Crimea, and then try to set up some kind unstable puppet in the East, which will not work and leave Germany stuck in a Super-Vietnam. Given that this is Nazi Germany, we could not rule out Germany throwing nukes against the Guerrillas.
It won't be dystopian, though. It'll just be a matter of some people really lose and some people don't. Ukranians, Russians, and other Slavs are going to get enslaved; the Poles are going to get wiped out, and Germany probably annexes Denmark, the Netherlands, and Germanizungs a bunch of territory.