Is there a way to control your NPC party members? Like make a party member move to a certain location, or have one party member attack one monster and another attack another?
At the moment no. They will stay in close proximity to you. Once you engage an enemy they go nuts. Usually though, I have noticed, if you have fighter henchmen it will attack what you attack.
What I thought was amusing was that in my last mission, my Stalker and the fighter henchman pretty much attacked the same creature I was attacking even in horde situations.