Personally, I'm pretty happy because Caliburs are my favorite swords in the whole game, but yeah, normal damage isn't as useful as it used to be.
The problem with the Leviathan Blade was that it pushed targets away before the damage could register. The new changes let me clear the Arcade with a lvl 1 sword—not THAT powerful, but still usable.
The Amputator soft rework is interesting, but just like with the CIV, maybe we could "standardize" the swords a bit. Bonus damage isn't that useful on weapons anyway, so we could leave that to armors.
My recommendations:
Amputator:
[-]Remove bonus damage against Slimes[+]Buff base damage (should be less than Levi)
CIV:
[-]Remove bonus damage against Undead[+]Good chance to inflict strong freeze[+]Buff base damage (should be less than Levi)
About Turbillion:
It's a pretty unique weapon and isn't intended to be OP. Changes are welcome, though many would agree that the small projectile hitbox and slow swing speed aren't great. There are many ways to fix this, but the simplest and most elegant solution (IMO) would be to add a small vortex effect, since it synergizes well with shock.