What is the universal move back key? I am still very new to this.
Whatever you set it up to be It's the key that makes all your characters move backwards together.

For me, all of my clones move together on an unmodified arrow key, so it'd be the down arrow key. I control individual drones with SHIFT-, CTRL- or ALT- modified arrow keys, and my main with QWEASD.

One of the biggest disadvantages for a multi-boxer is manoueverability (close second is situational awareness - I've often lost a clone to an unnoticed sap on the field of strife, but that's a whole different story ) and each of us has to find our own solution to it really.