The Defias Messenger got new information on upcoming mage changes on the Burning Crusade. Apparently the Water Elemental is not on a timer, and won't despawn on his own. It's not intended as a tank, but as a source of extra ranged DPS. This makes the reagent cost much more tolerable. Ice Lance is currently underperforming, and will probably be changed as well. Invisibility will wipe aggro, but the post doesn't say whether it can be used on raid bosses.