I have a set up that I enjoy on my 3 mages.

I have my 'F' key set to slave one macro to focus. 'G' set to slave two macro to focus and my NumPad 0 set to cast polymorph.

my macro is a simple one.

/assist NameofPlayer

/focus

then my polymorph casts on my focus targets after I cast it. I am at work so dont have the actual macros on hand tho.