Blunt damage only bleeds through parries on very low strength characters.
The purpose of the mechanic is to stop skinny mages with daggers from negating 100% of the damage from big heavy weapons like axes and hammers.
Of course it also results in the heavy greatblade which has a decent amount of blunt damage hitting through your parries as well, but no other swords should be hitting very significantly.
I believe the solution here is to reduce the pierce damage of the heavy greatblade as it is clearly the meta sword at the moment, and the other greatblades essentially don't get used ever.
It also makes sense for the pierce damage to be reduced as the curved blade should not have higher thrusting potential than the straight blades. This would result in more people choosing other swords over the heavy one as it wouldn't be the best choice for all situations anymore, meaning less people hitting mages for significant blunt damage through their parries with swords.
I'll admit this is a slight thread hijack to talk about weapon balance, but it also ties into the topic well enough and so I self absolve of any wrongdoing.