I play 2 casters so I initially ran into this problem also when one is not facing the right way.

I use Micah's multibox.

What I did was on CasterA I use the W, A, S, D keys to move and unbind my directional arrow keys.

On CasterB I unbind the W, A, S, D buttons and keep the directional arrow keys as is.

So, when I am playing on my main box if CasterB is facing the wrong way I just simply use the directional arrow buttons to turn him around(or move him) and it doesn't affect CasterA.

Also, I would not have the "/follow <name>" in your macro. What this would do is that once you get CasterB turned in the right direction(facing the mob), if CasterB is in front of CasterA, he would then turn around to face CasterA as soon as you hit the macro cause /follow always makes you face your target.

Hope that all makes sense.