This is basically "final form" of this build, where you keep high level elemental totem on switch (thanks to wizards path boots), and then use these free slots to get pierce for yourself, and boost path of flames + hive.
I think ideal but expensive combo would be two throwing xis knives with 2x ~-60 fire/poison, but range of rolls is high. Piranha swarm is basically a bad roll of these runewords.