Finally, a reply! Thank you, Herr Hinteler.
For my purposes, I am less concerned with determining Germanic tribal make-up than in distinguishing Germanic vs. non-Germanic (e.g. Celtic, Latin, Basque) genetic heritage. Perhaps I should clarify this by noting that modern national rivalries between France and Germany on the basis of supposed ethnic differences would prove amusingly ironic if the two peoples came largely from the same stock.
You say the Germans are less diluted. That may be so, but may I ask what basis you have for this assertion?
Brown and Black haired Germans seem more common today than the "Nordic" blonds of Tacitus' time:
"For myself, I concur in opinion with such as suppose the people of Germany never to have mingled by inter-marriages with other nations, but to have remained a people pure, and independent, and resembling none but themselves. Hence amongst such a mighty multitude of men, the same make and form is found in all, eyes stern and blue, yellow hair, huge bodies, but vigorous only in the first onset. Of pains and labour they are not equally patient, nor can they at all endure thrift and heat. To bear hunger and cold they are hardened by their climate and soil."
Of course, Roman historians may be prone to overgeneralization and to presenting rumor as fact, but the quote taken at face value suggests some substantial alterations since that time. I do not know whether immigration in more modern times is responsible, or intermixing in the shifting demographic migrations of late antiquity and early Middle Ages.