Ok so playing from the perspective of the slowest has given me some insight.

Apparently there is a 'drag' on the mouse broadcast when in GPU intensive fight, such as jailer / desecrator / frozen / plague sort of enemies. This results in some of the slaves only updating a little, slight behind the master. The problem is if I drag the mouse from the master out of any click-worthy areas (to escape), the slave goes halfway and winds up clicking on a click-worthy area. This results in the slave standing there attacking when the broadcast order was to move.

It can also be seen in some doorways like towers in A3. The GPU load definitely seems to be part of the problem.

It'd be good to know what GPU specs everyone is using that encounters the problem. I run a 480GTX non-SLI mode. Second 480 is for handling physX.