According to my experience as a destroyer, i'd say stick with focus until you actively start PvPing (atleast till high 60s). Also just posted a similar post about this, please do check it out, some valuable info in there.
criticals is everything in L2, later in the game your crits can do as much as 10 times the damage of a normal hit
the only real benefit you get out of increased attack speed is faster reuse on skills (Which on long reuse timers can make a decent difference)
just keep a dagger handy and equip that before you pop off a long reuse skill, its reuse timer will be based on your attack speed at the moment of usage