The pets don't do anything, Wingflier. They're kiwis.
The
minion AI got fixed before pvp came out (latency notwithstanding) for the zombies (who don't wander off into the middle of not-near-you anymore) and the spectres (who are still debateable in their worth really); the skeletons got minor fixes but since they don't last indefinitely they just wander near the summon point still. Zombies and Spectres now persist with you through zones and/or towns (unless you unsocket the relevant gem or move the item holding the gem, which kills them), and the basic summon zombie starts at 3, not 1.
If you aren't going to be a summonerish character, the zombies are a reasonable meatshield as long as you have corpses around (and mana to raise them, and the intelligence required for whatever level skill gem you want of it). If you focus on them more, they hit like a truck after a point (the skeletons are still fragile and work best in groups though), and are affected by auras if they're in range. Basically, the zombies can always be useful (though if you stop leveling up the skill gem they'll start getting one-shotted after you reach a harder difficulty), the skeletons are either cast a lot, often (or dumped into a spell totem-linked socket, which makes it more expensive but less clicky), and the spetres are still more or less bloody useless in melee, but reasonable as a ranged ghost.
