They maybe arn't overused, but it's maybe not only because oftheir stats but because of their requirements in STR, that not anyone can afford with their chosen build. And i still see some flamberge users who are doing relatively good, using the great range of the flamberge.
It's not because a top tier, thus very important upkeep item, is not so used, that you have to buffed it so that everyone uses it. If you have one and can't use it well, sell it and find another weapon, don't call for a "look at the difference, what shall we do ? Nerfing the GLB is ofc unacceptable, what shall we do then ?" topic.
And the unbalanced is a pretty hard malus btw.