Two other things to keep in mind...
1) Learn how to "pull," meaning when you see a large number of monsters, use a bow or wand and attack them, and walk back so they come to you.
2) Learn the mob structures, and know what to pull/aggro. When you see a huge mob, never rush in. Try to find a patrol in that mob, and pull it out first.
These two techniques are a must when playing with henchmen. And remember, Henchmen are only as smart as their leader.