Manolo and Jim,
I've handled a number of examples of the "Germanic" style of headsmans swords over the years, and although their intended use dictates that they be weighted in favor of the tip, they are by no means clubby or cumbersome. The swords tend to have a respectable distal taper, being quite stout at the forte and thin at the tip. Of course, they would not be as responsive as a combat sword, but having caused a fair amount of consternation at gun shows by wielding these (with owner's OK of course
) I wouldn't call them "useless" in a fight, either.
Keep in mind, as I have said, that continental headsmen cut with a horizontal stroke. I think that their swords were admirably designed for the function, and the fact that the blade format remained unchanged for centuries says something.
To do the grim job with a sword demands speed and accuracy; the weight of the weapon is secondary. Otherwise, an ax and block could be used, but that would be too "low-rent" for aristocratic convicts, wouldn't it?
Remember the stories of some of the Sanson family, who could cut so fast and sure that the head remained upright in place even after the follow-through of the swing was completed?