Just finished chapter 7 on MN and have experimented with Yakumo's weapons. I feel like it goes
>Toolbox
>Sword
>Staff
>Rapier
Toolbox has absurd AoE and high delimb rates to the point you can just cheese everything with bloodraven 360 and back-forward lights. Also even though it's got such a large range moveset, those range attacks do the same damage as melee weapons do.
Sword is the fastest and has the most natural feeling moveset while also having decent bloodraven attacks where it's not too uncommon to get fully charged swings out without being hit.
Staff base form is slow and doesn't cancel into shuriken very well because you have to wait for Yakumo to stop spinning it before he can shuriken, which takes forever. 360 moves on it are pretty good but it's bloodraven attacks are what carry it. Learn the release timing on each swing and you explode everything and get ridiculously fast guard breaking launchers with high delimb rate.
Rapier just feels like a worse sword and a worse bloodraven staff. Having to sit there holding attacks turns you into a sitting duck.

I've actually been going through mainly with Staff but if you are struggling, learn the toolbox weapon and you can breeze through the game.