On MASTER Difficulty:
Highly recommend taking out the scorch titans first & AT A DISTANCE. (Northstar works well here.)
After they are destroyed, start hitting Viper & move forward to trigger a checkpoint.
(use cover and strafe left & right during his missile barrage) You'll want to have a solid amount of life left at this point.
I suggest using the Expedition Loadout and spamming the lock on missiles (RB) in between volleys use your primary to keep shields down.
Once your core is charged switch over to the Tone Loadout for the Salvo Core. Unleash! Then swap back to Expedition missile spamming.
Rinse & repeat.
I tried all sorts of loadout combos and this particular one melted Viper in one run.