I don't think is OP for it, because:
1. Soul breaker can be completely blocked by pneuma+tatami skills.
2. High vit/high def means less damage from soul breaker(the str stat part), even with more spamming and doesn't miss due to int stats.
3. Soul breaker considered "ranged physical attack", not matk.
4. There's no linked buff for soul breaker, unlike sonic blow.
5. Suitable also for hybrid soul breaker sinx to "rearrange" their tactics :P