matter fact for a bowmerc ias doesnt really matter because you should be moving and by the time you are in range for the merc to shoot them they should be shooting them (enemy) once per teleport i'd reccomend getting some +skills
if you have +3 skill on a act 1 merc they emit a lightning spell that does approx 1600 dmg (b4 pvp reduction)
i have an act1merc with that i can demonstrate if you need =-)