Damage calculation

It takes all buffs and such into account before reducing the Def/Res for the special proc. Example. Moonbow on a 30 Set unit is like being hit with -9 Def, meaning the damage will be the Atk stat minus the new 21 Def for that one hit. Say that same unit gets Def tactic and Spur Def 3 (+10 total Def) (Def now 40 with buffs) then Moonbow will hit with now -12 Def, meaning the damage is now Atk minus the new 28 Def.

Hope this helped!

If it didn't take buffs into account, buffs would be useless. So yes, it does.