The accurascope becomes more useful when attacking boss mobs that are many levels above you.  At level 60 with maxxed out ranged weapon skill, the chance to miss another level 60 is seems to be around 99%.  When attacking a level 70 boss mob however, even with maxxed weapon skill accuracy can easily drop to 95%.  At this point adding +3% chance to hit is much more effective than +7 damage.

(300 dmg + 7 dmg)*(0.95) = 291.65 dmg (avg)
(300 dmg)*(0.95 + 0.03)  = 294 dmg (avg)

So, I would recommend an accurascope for 40 man raids, but for PvP the added damage may come out to be more useful.

-Arasi, Shadow Moon server