Updated with a new dedicated calculator to mathemathically see everything more advanced than overframe.
I think Previous forma setup should be fine.
Serration or Spectral Serration can be used over Bane mod for general lvl 100-500 Steel path.
Hellfire is 5% ahead of Thermite Rounds in terms of raw dmg & heat status priority.
A sick Heat riven with Multishot / Critical dmg would be the cream on top
Also feel free to test [Hunter Munitions] over [Hellfire] against Infested or generally. Its less dps but an interesting Option.