Hardcore WD running Helltooth build

Corpse Spiders - Medusa's Spiders
Wall of Zombies - Fire Wall
Acid Cloud - Slow Burn
Spirit Walk - Jaunt
Piranhas - Piranhado
Soul Harvest - Languish

Currently using Molten Wildabeest and Esoteric Alteration gems

Bane of the Trapped I'm assuming would be the best gem in this situation since I'm running cold skills and the cc from Piranhado?

BoT, Molten, Esoteric

There's no need for Medusa Spiders, when you hit with Acid Cloud for example, your HT 2 piece set bonus procs slow and necrosis effect, which also procs Bane of the Trapped.

Not necessarily using Medusa's to proc BoT, just using them as a safety net since 60% slow helps out a lot in HC, especially when my WD's toughness isn't the greatest yet.