In arena i would normaly just ignore him untill i have nuked down all his guys standing on a range.. that goes with rogues and warriors aswell.. then i would move over to the BG tack on killing those..
In BG (or as last in arena) i will deal with it by droping 4 fire nova totems and then 4x shock him.. that will normaly kill any mage or othere anoying melees that rund to much to get Lightening bolts going smoothly.. remeber to purge him just before the bomb and shocks... So.. drop bombs.. Purge then shock, if good timed that should leave around 10k in the same sec Follow up with 4 magma if its anything left...