for the arcane either use Secondary Encumber for more status effects or Secondary Shiver for more damage to enemies that are affected with cold the reason you use Secondary Shiver despite no cold status is since the [Epitaph] force procs cold on the radial shot

the exilus you can either put in [Pistol Ammo Mutation] (if you have trouble with ammo) or [Lethal Momentum] (to have the projectile travel faster) or you can just not run one and it would work perfectly fine

if you want to use zero forma you can get rid of the exilus and [Fulmination] then move [Amalgam Barrel Diffusion] to the polarity and put in [Pistol Elementalist] for the increased status damage