Laggeron:
No. There should not exist 'any' weapon that 1HKO a Boss.

But here a way to fix it:
-The normal hits deal in 90% of the time no damage, but in 10% it will deals 9 times the damage of a certain weapon. this would be tnough to kill the most of the enemies.
-The Charge attack deals no damage in 10%, but in 10% of the charges it will deal 10 times the damage of a certain weapon.
-also, the Charge attack should have a total Chance of 10% when all of the damage ticks did hit. so each single hit would be less than 10% Chance of course.

This would be a nice weapon to deal with menders.

Installer: +1
Yes, I like that concept except one thing: allow specialized damage, too. It would be a hard weapon to get ist mechanic learned, but beeing unpredictable is something that shines in PvP and I love the idea to place *mines* vs PvE

Aftermath:
It is also something similar to what I still got ony my list of unposted suggestions. But with a difference: instead of a Status (curse is still debatable strong), I would rather see a nice damage Output.

My suggestion:
Immagine a big rune similar to what a sealed sword creates with the range of a mist bomb mist radius. When that bomb explodes, it creates a curse mark to all Monsters inside the rune's range. After the Explosion, the rune will remain for a second on the floor, but only for visual purpose - it will not have any effect to Monsters who will walk over it after the Explosion.

The curse mark will work similar to a maskeraith curse (NOT the curse Status a faus may inflict) and after a certain time, the cursed Monster will recive damage, the 5 star Version may create even a Little AoE around each of the curse explosions.