You don't need the push command, I imagine this is what is causing your problems. The <tag> ("all" in your case) makes sure the command gets to "all" toons.

Just

/jamba-follow aftercombat on all

and

/jamba-follow aftercombat off all

should do the trick.

You need to make sure every toon has the "all" tag. I'm pretty sure thats a default.

Let me know if that works for you.