Onoki is purely about buffing strong fire/wind/earth ninja and providing that extra standard attack.

He is best used with for example Hokage/Jonin Minato, Susano Itachi, Sage Naruto, Masked Man.

I don't see much use of Onoki with your current ninjas unfortunately

I guess that's okay-ish

I'd use the Fire Enhacement buff with fire main though for the anbu itachi nuke.