I don't think you will find many times where you will want to type something on all of your guys at the same time. That said, maybe you will. Try it out for a while and see what happens. Personally, I like to be able to play all of my characters individually (for raids and such) so I don't change any of their bindings as you have done.

What you will find most boxers do, is they do not broadcast asdw, but DO broadcast the arrow keys, and the arrow keys are what they will use to break follow with their slaves. You will also want to be able to broadcast special strafe keys to all of your guys, as you will be strafing out of fires/lava/ice patches/all kinds of crazy stuff as you level, and having those buttons will be extremely helpful.

Really though, you will find as many ways to box as there are people on this board. Try it out - if it doesn't work, fix it. You'll find tons of good ideas here, but sometimes they won't fit your specific playstyle, so adjust them as you see fit.