On Toon A create 2 new macros
Name Toon A
/clearfocus
Name Toon B
/focus toon B

On Toon B create 2 new macros
Name Toon A
/focus Toon A
Name Toon B
/clearfocus

Then create the same macros on both Toons
/follow focus

and
/assist focus
/cast autoshot

You can put petattack in there but its not really necessary anymore since blizz changed pets to attack in Defensive mode.