Well thanks to the new Periapt of Clarity we can know 100% it's ninjutsu and not blackmagic.
So, Earth/Dark/Water/Ice Ninjutsu is pretty much our debuffs which is very very very hard to land on some of the higher Teirs.
You can get aceitics tonic, that helps sometimes
Can lower it's resistance with Elemental Ninjutsu's.
I tried looking into Magic Accuracy for Ninja, it's insanely limited minus doing Trial Katana's with Magic Accuracy.
Here's a decent set...
Ammo can be the Chakram from AV (+8 acc)
I have 2 MAB katana's which is +22INT together
Any other imputs about landing the debuffs accurately?