Unchained. Seriously, why are we not abusing this skill?

[JackFross]

so, unchained and berserk in defiance(without unchained) which one gives bigger boost to damage?

Unchained raises you from 75% to 100% (A buff of +33.3% damage - stronger than Fight or Flight!)
Berserk raises you from 75% to ~75%x150% = 112.5%

Maim and Storm's Eye make the difference larger.