short or medium maps
Early spear is fair play, but against chaos it may not work so well. Remember, chaos can start with an economic advantage with cats, and that will force you to either make a castle archer or swordwrath. If he matches you with a jugger, you're fighting a losing battle (especially against castle dead, the poison will force you to garrison, while juggs can regenerate health at center).
should pack mentality ever be used or is it pointless?
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.