I do use pack mentality sometimes, but you have to judge when it's best. If he's still using early archidon and swordwrath units, cats are fast and can clean house. If I still have 5-6 cats left after the starting skirmish for center control, I'll think about buying it, even if he has a castle archer. This is because I can run them behind a ghost or another jug. The castle archer will target the tank while my cats clean miners a few spaces away, out of the splash reach.
what if he has 2 or 3 castle archer as the second targets furthest away unit e.g. crawlers and the 3rd attacks randomly, and im not saying that a meatshield at the back to protect weaker units but 3 castle archer are invaluable against lots of crawlers and meat shield.