They only seem to attack monsters if you weapon attack them. If i'm using skills such as Flare, they won't start attacking until they get up close. Maybe have them start attacking whatever you use a damage dealing skill on a monster?
I've used this as a good thing, it allows you to pull enemies while soloing, which is good considering a lot of people complain that henchies attack anything that moves.
The problem with henchies is you cant take them with you to UW or fissue of Woe.. it shits me. Other then that they are really good as human shields.. :-)