I'm with Kazey on this one. Using it on CD as a mitigation ability could mean using it entirely when you didnt need it. Also if your doing this, you might as well let your healers know when its up so they can expect to heal a little less.
I like it like an ohcrap button for periods of time i know theres gonna be a lot of incoming damage or when i need to buy my healer sometime. On the opening of a pull to limit burst healing need so the healer can get in position and also have less initial heal agro, or when healers are silenced to limit incoming damage. Anything that will cause predictable burst dmg to you or periods of time your healer is busy/silenced/out of mana, are much uses for the ability imo.
Galushi - 85 Dwarf Warrior - Shadowsong US Alliance.
Branigan - 85 Goblin Warrior - Kilrogg US Horde.