Since the v.193 patch, there has been a bug with Hayato's Iaijutsu Phantom Blade ability, where casts will sometimes fail to deal damage, despite all visual effects registering.
If Phantom Blade casts are more frequent than once every 5 seconds, no damage will be dealt, despite visual effects all registering.
If Phantom Blade is spaced more than 5 seconds apart, it will work as intended.
Video of this bug:
Reproduction rate: Occurs 100% of the time when a sub 5 second interval is attempted.