It's kinda a risk/reward idea. You make yourself more vulnerable using this weapon and it can lead to death in certain situations, which wouldn't happen with a "normal" weapon. The reward is that you can deal a massive amount of damage. If it doesn't fit your play style, then this weapon is nothing for you, but it doesn't mean that this weapon is bad. Like it's already mentioned above in the wiki, the Souls games had always these kind of weapons, and like almost any other weapon in the Souls/Borne universe they all have their right to exist.