Hello there,
I would like to suggest few small changes which could help Kurotsuchi find a place on battlefield.

+1: Mystery causes slow down and suppresses immunity to 4 targets for 2 rounds.

+1: Gain one extra standard attack to 2 ninjas at random (cannot be overlapped)

+1: can be trigger twice

+1: Triggered at 10 combo, causes 5 combo to 4 random units.

+1: Increases Kurotsuchi´s ninjutsu by 25% for each earth ninja in lineup.

Chases gets only slight buff.
Since Kurotsuchi is support, 25% buff from passive wouldnt make a huge impact on game.
Giving extra attack to 2 targets instead of one can cause (if you are lucky) 3 ninjas getting standard attack. (1st increase hits Kurotsuchi + 1 other ninja, 2nd increase hits remaining 2 ninjas)
Mystery suppressing immunity and slowing down enemies for 2 rounds causing immune ninjas like Jinchuuriki (6p, Bee, Kushina etc.) losing edge of higher initiative players for following round. This would be another option to deal with faster opponents (aside from Kimono Shisui stacking and Kimono Itachi cooldown increase).
Such changes would provide players cheap or "poor man´s" way to affect game. (While still being countered by Fire, Earth and Water main directly and Katsuyu mystery summon, so the actual impact on game won´t be that dramatic.

Regards, BattleCrier