the issue here is when we are software boxing... when my cursor goes over a windows, and when I move the mouse to another window, the mouse pointer is very often on the edge of each wow window...

The best way to get the cursor at a precise x,y spot could be a script (or anything else) that moves the cursor itself from a location to another instantly .. each 0,1 sec the cursor would be placed on a specific spot on each wow window, then jump to another specific spot... this way each window would have the mouse in its center instead of its edge

no mouse movment, but a mouse jump .. I don't know if I'm understandable telling this ... but imagine that you switch your mouse from the wow1 windows to the wow2 windows at your maximum sliding speed ... the cursor could stay in the middle of the wow1 window, while you already can be at the middle of the second wow window ...

this piece of software wont be clicking or doing something illegal .. just shifting the mouse pointer from a position to another without any trail done almost instantly !!!
tac tac tac tac (0,4sec) ... the mouse centered (or wherever you can want to clic) itself into each wow window.. and you just have to cast your ground aoe spell and press the left clic binding to get it done !!! and this could be allowed because that's just a mouse positioning.

btw isn't it already doable with AutoHotKey ?