Against most pvp teams which uses a mystery barrier (like Sasuke, Gaara, Hashi), your barrier will never hold if they have their barrier on position 4 since their barrier will always override yours if they use it to counter your barrier.

If you use your barrier on round 2 or even 3 to override a position 4 barrier, you would miss out on your mystery. If not, your damage would be reduced by quite abit.