Note that if you want to use Corrosive + Heat, instead of Viral + Heat, you should remove [Hunter Munitions] for [High Voltage], and [Rime Rounds] for [Hellfire] or [Thermite Rounds]: [Hellfire] will give you more upfront damage, and make Heat higher in proc priority; [Thermite Rounds] will give you more Status Chance, and still have Heat higher than Corrosive in proc priority, but only slightly.
If you decide to go with [Hellfire] you'll need 1 more Forma; I recommend a "V" on Rime Rounds, since you might prefer Primed Shred, and you'll have it ready, but you'll also need a R4 Hellfire.

--Attention: If you do NOT have Primary Merciless (or Primary Dexterity, if you prefer) at least Rank 2, you'll still need Serration or Heavy Caliber; if you do NOT have both Galvanized Aptitude, and Primary Merciless (/Dexterity) you'll still need both [Serration] or [Heavy Caliber]. In both situations you should drop your Heat mod of choice ([Thermite Rounds] or [Hellfire]).

P.S.: In case you want to check the damage numbers, and only see 5.7k, click the "APPLY CONDITIONALS" slider. That will show you all the damage this monster does after you stack your Galvanized mods, and Arcane. You can then compare to the previous [Serration] + [Heavy Caliber] builds; just keep in mind [Hunter Munitions] gives you a bunch of Slash procs, and those don't show here!