Did some further testing with Winds of Retribution. MT'ing the temple x4 raid, the ability did effectively no damage the entire zone. The last 3 named mobs we killed (zone boss was not available), it did a total of 9k damage, about 30 dps. The fact that it only procs after wards means there will be a huge gap between [Solo with no merc] and [End Game Raid MT] where this ability is a waste of a prestige point if you have a half-decent shaman with you.