For what it's worth, I'm finding it to be a little flakey myself. I've been trying to force myself to get better with QoT, but the Shambler's response (or lack thereof) to the attack-move is quite frustrating at times. Sometimes, as best as I can tell, right before they're in range of the enemy, they stop, and the distance is just slighty (1, 2 pixels, maybe?) too far for them to actually attack. So they wind up sitting there until the enemy closes the distance. Or, if the target was Reg, he just sits there out of range and shoots them with impunity, until I notice it and force them to move closer and make them deliberately attack him.
I've been trying to get a better bead on this issue, and make the occurance repeatable, but no luck so far. Still, it would be nice to smooth it out, because it really is a crucial option for the Generals to have.