The word arcuarius should refer to a simple archer of the kind depicted on the Bayeux Tapestry, not a crossbowman. However, the two archers recorded in Domesday Book - both of continental origin - were too well-endowed to be simple archers: William held a modest estate as a tenant-in-chief in Hampshire, and Reginald was a minor tenant-in-chief, or sergeant, with two holdings among those of the king's ministers in Oxfordshire. It seems likely that they were crossbowmen.
Archery played an important role in the battle of Hastings, Harold's apparent shortage of archers probably being a significant factor in his defeat.
For further information, see Jim Bradbury, The medieval archer (1985).