I think random motions should just be active when there is nothing else going on. Maybe something like this:
1. if Exit is in Range - > Run towards exit
2. else if Monster is in Range -> Run away from closest monster
3. else if - has been dragged recently -> Keep running in the set direction for a while
4. else - stick together( with maybe some occasional random movement to keep them from just sitting in place)
That would make them kind of predictable but it would mean escape plans have a decent chance of working out :)