Hi

i also added a arcane mage to my mboxing team and i just use this simple macro

/castsequence [target=focustarget] reset=combat/12 [nochanneling] Arcane blast, Arcane blast,Arcane blast,Arcane blast,Arcane missiles
/use Mirror
/use Arcane Power

and i do nearly 2,5-3k dps. hope this helps a bit.