Get Damage shield pots, clickies, etc. Equip some sort of non-weapon in both primary and secondary (to avoid ripostes). Go to a zone that has mobs that will aggro on your warrior, and not run at low health. Use the damage shield to kill the mobs on your warrior, but do one point of damage to each mob with the mage (mage should not be grouped with your warrior). As long as your mage does at least 1 point of damage, and the warrior does no damage, your mage will get all of the XP.