One thing I noticed when using weapons from the Cutter series is that the ghost strikes usually miss after the first time, so the attack pattern is like this:

Hit 1
Ghost Hit 1
Hit 2
miss
Hit 3
miss
and so on

This leaves the cutter series with much less practical damage per second than other normal swords, making it only useful for stationary enemies and enemies you've pushed up against walls. The knockback should either be lowered or changed so that the second strike gives the knockback, and the first moves forward. That way both hits would connect, you'd get the same knockback and the 1 block movement would position you where you need to be for the next strike.

This series already has a ton of flaws, despite it being really fun to play. It'd be sufficient to have at least this fixed. :)