I've used this before with AHK.. it's not perfect but it worked. I would hit a key so all clients were in the same camera view and then hit CTRL-z to do the aoe. Each client needs to be maximized as AHK won't send to minimized windows

~^z::
keyWait, ^, z
IfWinActive, World of Warcraft
{
MouseGetPos, x, y
ControlSend,, {Ctrl down}z{Ctrl up}, ahk_id %wowid1%
ControlClick Xx Yy, ahk_id %wowid1%
ControlSend,, {Ctrl down}z{Ctrl up}, ahk_id %wowid2%
ControlClick Xx Yy, ahk_id %wowid2%
Return
}