It has 2 lenght and 3 swing damage less. How is it 'a nodachi with thrust' ? Doens't make sense at all. Jesus.
Because if you've ever seen anyone use a nodachi effectively, they do so by making weapon stun a core part of their playstyle. The fact that it can be said that the nodachi is viable due to it being effective vs longswords(light weapons, really), is a point in its favor, not some obscure bs that shouldn't be considered in balance. The idea that every weapon should be equally as good as the next in either the same type or amount of situations, is boring and not what anyone actually wants (it's also not how crpg has ever been balanced.)
Yes, the HGS is probably the most underpowered/underwhelming weapon of the 2h sword line-up, but please take a second to actually compare the stats to a few other weapons, particularly the Danish Greatsword. Whether or not people actually utilize the HGS to its full potential does in no way affect what the actual potential of the weapon is.
Of all the issues the HGS has, the main thing holding it back is how easy it is to read (big thick, shiny model).