Does anyone know about pre-schism German saints?
First, just want to note that the geographical area we now call Germany was a diverse, ever-changing expanse of many different kingdoms, ethnic tribes & massive conquests/invasions during the Roman, Late Antique and Early Medieval period.
In part because of that, there aren't tons of pre-schism "German" saints that I can think of. The Vandals and Visigoths, for example, were Germanic pagans who eventually converted to Arian Christianity. The Lombards were a mix of pagans and Arians, but became orthodox Christians in the 7th century very gradually (by that time, they had crossed the Alps and taken Northern Italy from the Byzantines). The continental Saxons were largely pagans until the 8th century.
The one exception I can think of would be the Franks. Although some people think of the Franks as "French", especially because they eventually controlled most of modern-day France, they were actually a West Germanic people, originally based around the Lower Rhine.
In the 6th century, King Clovis, a Frank, converted from Germanic paganism to orthodox Christianity, and then started kicking butt, taking names -- that kind of thing -- and established a sizable kingdom. According to St. Gregory of Tours, Clovis became so powerful he was made a consul of the Roman Empire by the Emperor in Constantinople.
Anyway, there probably are some saints in the offshoots of Clovis' kingdom, but I don't know of any. I do know that the Germanic Saxon kingdoms in the modern-day UK sent a number of missionaries to pagan Saxon kingdoms in modern-day Germany. A number of those missionaries are saints.
The most famous of those is St. Boniface, who brought Christianity to Frisia and many other tribal Saxon kingdoms, and who is listed in some Orthodox synaxaria. St. Boniface worked under the patronage of the Franks/Carolingians, which helped in the expansion, b/c the Carolingians were kicking butt and taking names as they expanded their realm over the Saxons.
Other than that, for simply being extremely interesting, there's always Hildegard von Bingen, who is probably one of the most prolific, well educated and unusual female mystics in Christendom. Technically, she lived after the Great Schism, but before the Fourth Crusade, so one could argue that she makes the cut. ;-)