Obviously someone has never gotten a boss to a sliver of health just to have something go wrong. I for one keep my Fireborn active only if I feel it's needed. If we have another Warlock with it I switch to Song of Flame. Then I activate and call out "Grenades for everybody! He gets a grenade. She gets a grenade. You get a grenade." Oprah Winfrey style. Never underestimate the power of three guardians tossing 'nades every other second.