i always thought, that the problem lies within the fact that the core of the gameplay consists of getting around the parry window of your opponent, not the parry box itself. this places a lot of importance on timing, not on precision and outplaying the opponent.
i always imagined, that it would be better, if the parries could be held, but the parry box would only be as big as the weapon (or slightly larger) and that the parry would have a turncap and a cooldown. this without stamina loss.
right now, if an opponent parries at chest level and i attack the legs, the strike almost always still gets parried. if i try to circle around an opponent and try to hit them in the side, the parry box is still so large that i get parried most of the time.
but if an opponent could hold a parry, but the parry has a turncap, i could maybe trick them into thinking i am going for a head hit, but really trying to hit their legs. feints could be used to either bait out the parry...