The Germans did not use the flamethrower too much on the Western Front except in the early invasion of France and Holland. The flamethrower was used throughout the war in Russia and at Stalingrad during the initial siege. Not too much in Berlin or later in Stalingrad becuase of fuel shortages. The German Flamethrower, Flammenwerfer 35, used about a liter of gasoline per second. So at times where there was not enough fuel for vehicles, the flamethrower was consider a luxury.
The Germans mostly used their flamethrowers as a siege weapon, to clear out buildings and fortifications. They were used extensively in Poland during both the Warsaw Ghetto uprisings and later the Warsaw City revolt. BTW, two good movies that show German Flamethrower troops are the "Pianist" and "Uprising".
WWI is a different story and I would except to see a German Flamethrower in a future release.
Ken