They could have made nin's use blunt daggers. That would have made just as much sense. Besides, I see no reason why the number of piercing, slashing, and blunt users needs to be balanced, and nowhere is it written that it should or will. And making a dps, that should obviously use piercing damage, blunt, just for shits and giggles, rather than adding something that makes sense as being a blunt user, is just.... silly.