Tank: Only use LB3 and only when everyone but you and a healer is dead. NEVER use it on a special raid wide tankbuster talked about in a live letter
DPS: never, but especially NOT when the boss is at 0.1% and the enrage is next GCD
Healer: on pull. Every time. Especially if at max health. NEVER, EVER use it if you’re the last one up

Wait... this isn’t the thread for how it’s actually used? But for how it should be used? Just flip the logic on everything above...