For my reference.
Base * WeaponFinisherMult * (1 + Finishing Touch + Covert Lethality + Fatal Teleport*AbilityStrength) * (1 + Radiant Finish*AbilityStrength) * (1 + Savage Silence*AbilityStrength)†
...where mods correspond to their "Additional Damage" value (e.g. maxed Finishing Touch yields +0.6)
† Note that the values listed in the augmented ability tooltips are confusing. The value listed for Silence is the total multiplier, i.e.
(100% + Mod*Strength)
The augmented tooltips for Silence and Teleport intuitively label these values "Finisher Damage" and "Extra Damage" respectively, but the Radial Howl tooltip is labelled "Finisher Damage" while the displayed value is actually extra damage.