There is no way to target an AoE spell through an addon, macro or script without hacking. They removed the last option to do this in one of the previous 2.x patches. You can, however, use anything that does mouseclick broadcasting (e.g.: octopus, keyclone(I think), wireless mice, hardware mice splitters, etc.) to effectively click the same spot on the screen to do simultaneous AoE targeted casts, though you'll need to correct for camera angle differences to ensure you're all looking in the same direction when you do it to ensure they land in the same spot. Look up the "/script SetView"command and that should get you one option for doing this.