hmm the only problem I can see atm is potentially lag.. :S basically I am trying to use a similar thing for my team (freeing up focus for targeting) what i have noticed is that when assigning the focus it helps to doubletap it.. i know this could get annoying but try it and see what happens..

The reason I think it might just be that is that sometimes when I'm casting away it takes a sec for my clones to react to the command i gave them.. often choosing the new target to attack after they have begun casting a spell on the previous target.. I put this down to some lag problems.. even tho the macro is executed line by line.. the /cast command seems often to arrive prior to the targeting command :S the same might be true for the /focus coming before the /target/assist

anyways hope that helps.. I might have missed something silly mind you.. gl!

Edit.. also i would remove the clearfocus from your follow macro.. trust me it will get annoying.. as a mage you will be moving alot.. if you blink you have to reassign focuses etc.. if at all put the /clearfocus command at the start of the focus macro.. thus clearing any focus prior to applying a new one