As you know AS can be used freely during PvP even if u have 0 conceal. But you can not use it in PvM as the monster sees you.
I think AS should be done only if your conceal is greater than other sides perception or conceal should have a high bonus for AS. OR can someone explain me why is that different for PvP and PvM? OR If i have enough conceal i must be able to AS again in PvM too like PvP.
Hope this will be fixed in next patch.