Weapon DMG modifiers affect DMG from Skills?

Does the "15% DMG" modifier take place AFTER the skill dmg has been dealt or prior?

In other words; I have equiped a max dmg axe and just meet requirements, i cast Decapitate (+5...41 damage) and assuming the foe takes full dmg, will i be dealing 6...28 +15% + 5...41 or would it be 6...28+5...41+15%?

Only affects base.

just the base damage as D Fault has already stated....