All Other = everyone in that ATG, with the exception of the current character.

I usually create as many ATG's as I need, so that I send something to all of, whatever ATG.
You can add/remove toons from an ATG on the fly, via a mapped key too.

There are superior round-robin options coming, in a future build.
I believe you can get the tester version from Lax in the IRC.

At the moment, I round-robin via one step per person in the round-robin.