I actually think it would be cool to have multiple types of behaviour, with the specific behaviour chosen by a number of factors.

I can think of a number of ways for them to behave:

- Protect the Leader - monsters stay close to their leader, taking on a protective formation. Smarter beings would shift to protect the side from which danger is coming, whereas less intelligent would just huddle in a circle.
- Lone Wolf - monster will explore on their own, despite having a leader, occasionally coming back to the leader, and will freely attack if an enemy approaches. This mode would also apply to leaderless beings.
- Scouting Party - somewhat like the lone wolf, but will group together into a collection of, say, four beings, who would constantly move around the level to any location they can find. Rarely stay in a single place, will tend to retreat to leader if confronted but will fight if cornered or attacked heavily.
- Attack Formation - rather than surrounding the leader, as with Protect the Leader, they instead will position themselves to be able to attack threats collectively.
- Patrol - moving through set paths most of the time, beings with this set will be positioned within earshot of the leader, and will serve as warning, as well as attacking any foe that may come near.

Leaders would tend to position themselves behind their minions (unless surrounded in a Protect the Leader), and their minions would adjust formation or mode when near the leader. They will tend to remain in Protect the Leader mode with some patrollers in the nearby corridors and rooms, unless a threat of some sort is detected, in which case they're more likely to go into attack formation (it is possible for some to be in attack formation while others are in Protect the Leader formation, etc).

Might be a bit more complicated to implement though. Hmm.

Could be a nice addition still.