They could do something to combine disharmony with the fear line.
Let's say that disharmony has a 25% chance to trigger an hostile nano in the fight target NCU. At that point, whatever his level (except specific encounters) the NPC become open to the fear nano.
The logic would be that the hits of the Martial artist desorient the target and make it more vulnerable to fear...
I also like the idea to put the disharmony damage proc to be nano damage based, that way it can't be abused like it was after the nano damage change (900 to nearly 2k heals were a bit too insane)