Exploring my mind

Somehow I discussed with my friends about gregarious animals. If these animals were attacked, they would keep together. Somehow I thought it would be better for many situations to disperse e.g. if the animals would attack something.
I don't know who mentioned it, but we thought about this situation in computer games. Actually this system would be reversed: If a group of creatures would be attacked they would not stay together because the enemies could cause splash damage. And if they would attack someone they would stay together.(I did have an argument for this one but I don't remember it)