I agree, they are really underpowered compared to glaives, poleaxes, and all the 2 directional polearms. All of those weapon types do 5-10 more cut/pierce damage on their attacks, bust shields, rear cav, and half of them are way longer than any greatsword except on the stab, but polearm stab is instant so its even better.
Nerf polearms, buff great swords.