Keep your Arc Soul, put on some Karnstein Armlets for super quick grenades/melee/rift regen. Throw a Riskrunner into the mix and mow down everyone, see the nice thing about Riskrunner with a Arc subclass means you are able to trigger it yourself. If no enemies are proccing Arc Conductor for you then just throw a grenade down at your feet, you take only a small amount of damage and get Arc Conductor going, then you maintain it by killing all the enemies. Unlimited ammo, arc damage jumping between enemies, lots of ability regen. Having Riskrunner as a Stormcaller is like having a mini Stormtrance ready to go at all times.

You could try the Nezarec's Sin that Xur is selling.

I actually prefer VoidWalker in the raid over Storm. VoidWalker is better for dogs and Calus DPS. I do switch to Storm during Baths for the adds that spawn while dps.