While the RTS method works, I'm working on a game that doesn't have the objects close in formation. The objects go towards a player, so if they are far away, they won't go near the player because they stay in formation.
I never realised you can pick out instances like that. I got a method that kinda sorta works like this:
+Sprite1: On collision with Sprite1
+System: Pick Sprite1 instance 0
Move Forward 5 pixels
+System: Pick Sprite1 instance 1
Move Forward -5 pixels
Everynow and then they go over each other but most of the time they don't.
@Sargas Your method does a good job, although I noticed some times the objects struggling to move when bunched together. :/