Since it does tremendous single damage, use it on mini-bosses. Just dash attack targets, then slash into the air, do a couple airhits and summer salt hit them on the way down. Or just dashattack and dash away depending on the miniboss.
Harvester: For everything else. You can round up the mobs and spam Deaths Rage (?) with the Harvestor (RB+Y) and tornado them around you. You can spam this without taking any damage and anything getting close gets sucked into it. Rince repeat for TON of s