First, I would suggest a survey of the top assassins would reveal that nerve is relatively unused in pk. If that bears out, I would posit its relative unuse due to
- 2 rounds lag (1.5 with edge)
- minimal maladiction granted
- maladiction is random, thereby not necessarily targeting desired stat


Second, I would say that an enhanced nerve skill would help assassins fight shapeshifters, whom are largely protected against assassins by hard-coded arbitrary conditions (You can apply kotegaeshi to a fire giant but not a gorilla, but good luck assassinating a komodo dragon); other classes can be hampered far more efficiently using the other tools in the assassin toolkit.


Third, my proposal would NOT make nerve combinations an effective strategy against melee classes, whom can both lag and evade attacks and thus disrupt the combinations.