Of course the curse was overkill but overkill but of course Murphy’s law is not just for simple mortals:
Against anything human, more than one round to the head would be overkill: When the merely mortal goes up against the supernatural, there’s no such thing as overkill.
But there is a more important reason. The whole exercise had more functions than just kill a bunch of enemies. It was a show of power. It had to be not just sufficient but awe inspiring.
It was a bonding experience. A big party and the sacrifices were part of the fun. That is what people used to do at parties, they sacrificed creatures to eat.
And bringing in loads of sacrifices showed that the red king was a good provider. A wealthy and generous king. The right king for the red court.