In the description, shock debuff states that it has 70% chance to reduce power by 3 every turn. I have tested it with magus shinobi's power move several times. It NEVER reduces power. She puts upto 3 shock effects on all enemies. Each effect should have 70% chance but it never triggers.

(It also states that shock has 25% chance to remove golden effects. I haven't tested whether this is working as intended or not. )