Pets have various AI states (aggressive, defensive), plus the ability to trigger specific abilities.
There's is a distinct pet associated with each of the spec lines. Long-ranged specialists will have a 'brawler' squig, skirmish pets have shoot-and-scoot abilities, and the close-attack specialist will get a PBAoE "farting" pet. The White Lion will have similar pet specializations ... though likely no farting great cats. The White Lion, unlike the Herder, is a brawler aided by a pet. About this class, Adam says, "The pet's attacks work a lot like a Chaos Marauder's. The Lion himself debuffs his targets so the pet can do more damage. He has a pet that can distract his targets so he can move around and do more situational damage. He has abilities where he can do wide sweeps, his pet will attack his target and he'll attack his pet's target, and they'll cross over. Classes with pets tradeoff by being slightly less effective on their own. Without their pet they're not nearly as effective as the classes that don't have one." A favorite White Lion ability: the pet runs up to an opponent and then tosses him backwards into the air to land at the player's feet for easy melee. The designers are very much aiming to have pets usable in every situation.