You can use either targetoftarget, focus, or in your slaves/alts macro just add /assist party1. There are plenty of ways to do this, plenty of posts in the forums. As for you being a Mage's wet dream, just have a 'scatter' key binding. A key that is bound to a different movement direction on all of your characters. Eg, when I press Ctrl Q all of my characters move outwards/backwards/forwards.