There are other ways to initiate a battle aside from using a long bow

Regarding other classes: you do not need a special type of build to use henchmen effectively, the biggest advantage of the mabinogi heroes gold Ranger is the ability to attract and pull groups from a long distance (the long bow is the king for distance).

That said, one strategy would be to equip a long bow on your character as a switch weapon for the sole purpose of activating a group of foes.

Once activated the strategy becomes the same: keep yourself alive, direct your henchman appropriately. You don't even need a good long bow any old long bow will work. There are other ways to initiate a battle aside from using a long bow. 

Before the “AI” update I played though all the missions as an element list Nuker. For those who play this class effectively, you know that you want the tanks, when feasible, to initiate contact with the enemy. Thus leading with a longbow is not such a good idea. 

Instead, the key here is to push the warriors into battle ahead of you, gathering argo. The key here is calling your target. 

Basically, if you don’t know what role the henchmen are to play then don’t be surprised when their actions and attacks seem random and disjointed.