[Crannogman]

I have heard it posited that the German expenditures on their U-boat fleet led to a vastly disproportionate response in Allied investment in ASW - that the net effect was to actually dilute the Allied war effort more than the Axis's. In that respect, it was a reasonably-effective form of asymmetrical warfare. I don't have hard numbers, but I recall the ratio of resources committed by each side to be greater than 3:1 for the Allies.

That said, you are likely right that Germany could have pursued more beneficial routes to success