Viral+Heat is currently the absolute best combination due to the mechanics of how Viral functions at this current point in time plus Heat's infinite stacking nature of its application, and not just on [Regulators] but on just about all weapons generally. On Steel Path, even without taking into account that Heat provides an insanely economic flat -50% off of a target's current armour value, Viral ensures that Grineer will never be a problem, so [Corrosive Projection] isn't actually mandatory, however it is still one of the best choices of aura to run with this elemental setup. This build assumes Arcane Precision, as all [Mesa] builds should.

Electing to run two status+elemental damage mods instead of one status+elemental damage and one purely elemental damage mod will require a fourth forma, but does bring the status chance up from 24% to 30% and weights the ratio of Viral to Heat procs more in Heat's favour, which in turn would likely on paper result in higher DPS long-term on extremely spongey enemies. However, due to the sheer speed at which enemies will melt infront of you, rarely does this circumstance arise, even in Steel Path. Whether you choose to make this change or not is purely up to personal preference and functionally makes no difference outside of the most extreme fringe cases.