User blog comment:B214/Light Novel Volume 16 spoilers/@comment-95.251.22.158-20131226161918/@comment-16281343-20131227154057

The Longinus possesors are the one who need to be strong enough to fight or maybe even kill a god. Not all the members of the Rookies Four.

And just like what happened in the Rating Game of Rias and Sona, and just like what B said, there are rules that can hinder a team if they cannot adapt to it.