if you are in a BG where you are not alone and you jump a mage and if that mage puts frost armor up, change target cuz the slow effect from the mage's Frost Armor makes Fingers of frost proc and that can cause you trouble so just drop the mage down until he puts it up (if at all) and then just swap target and let some caster finish him off since he doesnt have the 50% magic effect reduction from mage armor anymore