Priests have the crappiest mana efficiency/regeneration of all four PvP healers. Basically, we need Mana Burn, because in an all-out efficiency battle, we OOM while Shamans, Druids, and Paladins still have over 50% of their mana bars.Originally Posted by Elanale
And like other people stated, only really bad players get OOM'd fast. In fact, it's pretty much impossible to OOM a Resto Druid. Resto Shamans are also pretty hard to OOM, due to Water Shield.
The only class I actually bother Mana Burning is Paladins, since once they're OOM, they can't cast a heal; in the case of Resto Druids and Resto Shamans, they can still pretty much cast heals if you aren't chain casting Mana Burn on them after they're OOM.