[Autumn]

These weapons are definitely a victim of seemingly careless scaling decisions and the fact that elemental damage is wholly inferior to the physical-type trio.

Until those two issues are fixed though, the dagger set could definitely be changed to deal piercing/slashing damage with better scaling while weakening their set effects to compensate. 80 GUI / 15 STR for the Hikage and 80 GUI / 15 VIT for the Tsukikage, while turning the Tsukikage's critical effect to FP reduction instead of Silence, and changing the back-teleport to only take effect if the attacker is in one range, otherwise it teleports to the closest cardinal square to the enemy.

Most of that sounds fine except the teleport effect change.

Here's what I'd suggest, due to a new toggleable skill everyone gets called Limit Potential, you could arguably move the water/fire damage to the potentials of the weapons, requiring and changing the other's damage type as well.

You could then tie the burn and silence procs to the water/fire damage as well, to give merit to the fire/water damage.