Heat bonus recommended for maximum damage.
This weapon has rather insane status output, quickly reaching the Viral proc cap of 10. Beyond that further Viral procs don't increase damage. Heat procs on the other hand deal 0.5 × (1 + HeatMods) damage normalized to BaseDMG, which becomes 0.5×2.65 = 1.325x, which is (5.175/3.85=1.344) +34.4% multiplicative damage PER TICK(×6 ticks).
So because Heat procs offer a very significant increase in DPS the build tries to bias status as much as possible toward Heat by using [Primed Heated Charge] and a Heat bonus.
As a bonus, the Heat procs also increase the AoE effectiveness of [Kuva Nukor]; shooting for a second, stacking up Heat procs on the primary and secondary target before they start ticking damage means that you have a higher likelyhood of killing secondary targets with the same shots you killed the primary target with.

Riven stat priority: FR > MS = CC > CD > Dmg = Toxin/Cold
CD > CC for use with Arcane Avenger.
Riven replaces mods with same stats. 6060Toxin, Cold and LethalTorrent being best candidates for replacement. If your Riven isn't 3 positives, one of which is Tox, Cold or FR, and has a negative then it's probably not even worth using. That's the reality of most 0.5 Dispo weapons.

[Reflex Draw](Holster Speed) is another good option for the Exilus slot.

Check out my other builds on my profile. Especially the "Generic" build series, which show the optimal builds for 90+% of weapons of that type.