I tried both good and evil archers. Racked up some fifty some kills with the archer and no achievement unlocked. I just tried the hobbit area and popped about a hundred plus hobbits heads off with the fire arrow and EA is giving me no love with no achievement unlocked.
If you haven't signed up for this, you really need to. You can get this awesome gamercard that you can use in forums or for anywhere else that ranks you in America.