Double Strike question

Is this :
"Performs two fast attacks on target enemy with your main hand melee weapon."
mean that DS did double of the shown dmg on the bar?

almost!

I think its close to 2x your onscreen dps
not realy know, look at the normal attack, if its close to a unlinked double strike*0.7
then you listed dps = 50% of effective dps

what matters is, dual wield

your aps, is listed as a avg aps (from the dual wield)
your double strike aps, is based upon mainhand only (when that is not listed on your tooltip)

double strike dual wield allow you to use offweapons, with any weapon stats, that not interfear with your mainhand weapon aps/dps