I had that exact same question!! from what I have gathered, it is delayed which is nice - would hate to lose the auto attack. This is only for melee, for spell weapon auto attacks they fire off right after casting a spell so casters don't need to time their auto attacks further favoring ranged/caster dps.

Also on the DPS front, I would doing I would have to guess (didn't parse leveling up) maybe 50k dps total at lvl 90. The gear scaling and monster difficulty ramps up to insane levels thereafter. So I wouldn't be too worried about that.
Additionally well geared players parse easily 500-600k each and much higher when burning so I still have a long ways to go to being up there. The 1.4mil is all 6 players in the group combined.