This [Pox] build is not supposed to be used as a primary method of killing a target but rather a back up against something that is hard to kill or an enemy you cannot easily kill with your primary or secondary. I prefer to keep the elemental combo this way so you can easily deal with groups of enemies in one or two shots. There are some mods you can change out if you have a different preference or play style

[Fulmination] allows you to hit more enemies but if you want to swap that out, you can put another elemental mod so you can add more damage.

The multishot mods are very powerful and in this case, you are guaranteed to throw two projectiles and a 20% chance to throw a third one at the same time. This will allow you to proc the enemies with more status and damage them more.

[Ice Storm] allows you to throw 6 poxes in a magazine compared to 4 without it. This is a personal preference, but if you want more DPS then you can replace it with a 90 cold mod. Having [Ice Storm] just give the fire rate from [Lethal Torrent] more value.

Exilus mod slot can either have [Lethal Momentum] (increase projectile speed) or [Pistol Ammo Mutation] (get more ammo). This is based on player preference but you will have to forma it if you want it bad.