So at first I thought I hated my double attack dagger but I think I'm changing my view.
dagger + atheling + twilight + epona's + brutal is 23% + a degraded sabre dance (20%) is an obscene 43% double attack rate.
Now for the meat of this: when double attacking so frequently would crit dmg + 20% out do 15% triple attack?
I'm assuming there are a lot of maths to decide the winner.. but at least my dagger seems to be contributing finally.