I just want to confirm for anyone that is unsure or does not believe it...
This grip DOES add double attack without warrior sub or brutal earring.
I was fighting as my drg/whm with this grip and i double attacked a few times
Any %+ to a job trait means that that job trait kicks in x% of the time.. so fast cast, triple attack, double attack, ect. all kick in with just +x% gear on.