AA question for dual wielders

[r0xx0r]

I've heard rumor of all kinds of things having to do with Sinister Strikes AA (Gates of Discord) 12 aa's to get rank 1 which is the only rank. Now i've heard that your offhand weapon acts like it's -1 base dmg then normal, and sinister strike fixes that. I've also heard that it makes it more powerful than it's base dmg, anyone know for sure what it is? cuz i look for it on alla or casters, even lucy and it just says what it does in game. Anyone got a clue?