I had the same experience with the Magic Archer and changed out of it in a hurry. To lock on to a Cyclops eye without switching to its shoulder or chest, I had to let the thing get within ten feet. I was wondering if the damage output would be better coming from the Mage - Sorcerer - Magic Archer path.
I tried it out after Strider - Assassin - Ranger and just figured my damage output was low because I hadn't taken any vocations that pumped up the Magic Attack stat.
Magic Archers are great against Harpy infested areas though. Having the assassin (?) effect that increases damage to enemies not in their fighting stance seems to help damage output when you can catch the enemy unaware, but then you're back to bug bites against whatever the opening salvo didn't kill.
The assassin vocation is really versatile, and a lot of fun to use, but it is probably a good idea to have the Strider's Leg Strength effect to balance out the extra weight you'll get from stocking a full kit of Daggers, Shortbow, Shield, and Sword.