Have you EVER , and I meant EVER, used this spell DURING a boss encounter, ie. in combat.
As holy/shadow or even disciplin doesn't matter, but I came to think about it. I haven't used it since level 70...
Hymn of Hope
Channeled - 5 min cooldown
You recite a Holy hymn of Hope, restoring 2% mana every 2 sec to all party members within 40 yards. Lasts 8 sec. The Priest must channel to keep the hymn active.