/cast [target=toonA, combat, dead][target=toonB, combat, dead][target=toonC, combat, dead][target=toonD, combat, dead] Rebirth; [target=toonA, dead][target=toonB, dead][target=toonC, dead][target=toonD, dead] Revive

this will cast rebirth in combat and revive out of combat. also, it will go down the list of toons. if you have more than one druid, its best to set different buttons for each druid to rez, especially while in combat, as each rebirth has a 20 minute cooldown.