They won’t auto-attack anymore.
So if you start a fight and they’re in Passive, or switch them to Passive during any point in the combat, they’ll stay that way until combat drops. If you try to switch them to Defensive, they won’t defend you. They won’t attack. Not until the fight is over, then the new stance will go into effect.
Now, if you switch them to Aggressive, something interesting happens. The Imp will fire off 1 Firebolt and then stop. But if you keep switching Passive to Aggressive, each time he’ll cast once and stop. But even that’s inconsistent. Sometimes he won’t even do that. You can also manually use the Firebolt skill. But he won’t keep casting. Using the Attack button or a /petattack macro does nothing.
The voidwalker is functioning in a similar manner. Like the Imp who does a single firebolt and stops, the voidwalker will do a single hit…he doesn’t actually engage the enemy. If I run away, the vw follows me. He doesn’t keep fighting the mob (though he’ll hit it if it stays in range). But if I fear it and order him to attack, he’ll run at it, hit it once, and run back to me.
So something funky is going on switching between stances during combat. It doesn’t work right. I assume it’s a bug because the minions give their message about attacking But they don’t actually attack.