Thief is probably the best class if you want to go for the archetypal archer.
Agility and cunning are probably the best stats to spec into(agility adding accuracy and cunning adding critical chance and effectiveness and willpower for magic damage)
as for powers it’s hard to say because I personally don’t normally play thief, however last time I checked shell cracker is a good power to have because it makes enemies take more damage after you hit them with it. As for magical damage you can’t go wrong with charge weapon. It automatically adds magical holy damage to your attacks at the start of a fight