It is painful trying to search for an answer on it...heck, even what it affects often results in conflicting answers, meh.
Probably one of those things where you'd need to grab a friend and do some low damage simple/unbuffed attacks and manually parse the combatlog using the relevant formulas to see whether it was applied before or after weapon power.
"Wheeeee, this is kind of fun. Oopsie...my bad." Fleet Admiral Geist, Klingon Science Officer
Arcadia, Benthan Assault Cruiser