Best bet is to just move a bit after you turn, to make the follower turn. You soon get used to making some unusual arcing movements for positioning ahead of a fight.

You can also map movement keys just to the second instance of WoW. I use QWEASD for moving my main (and the mouse, of course) and the arrow keys for turning / moving my drones when I need to.

But I rarely actually need to, except when they lose follow entering an instance or get themselves stuck.