Al'ar: Finally, a use for troll priests

There's been a controversy brewing on my realm forums over whether something is an exploit, a bug, or merely a creative use of game mechanics, so I thought I'd take the question (and the strategy) to the wider world of WoW blogs.

Basically, Horde guilds across several realms have discovered that by using a troll priest on the Al'ar fight, you can take off 20 percent of the boss's health in Phase 2. It appears that the troll priest racial ability Hex of Weakness, which decreases healing done to the target by 20 percent, makes Al'ar resurrect from his Phase One "death" with only 80 percent of his maximum health. There have been a few posts about this on Raids and Dungeons and Bosskillers, but it doesn't appear that it's a widely used strategy.

Vendetta, the guild on my realm that used this strategy for their first kill, said they don't believe it's an exploit, and that they felt they could kill Al'ar without using it. "Until Blizzard says otherwise on Raids and Dungeons or contacts us in-game, it's working as intended because the Rising Phoenix ability is a heal effect," a guild member said. Other people have compared it to using Divine Intervention on Razorgore, which was deemed an exploit, and the bugs that caused Vashj to lose 20 percent of her health before 2.1, which were not.

So, raiders of the world, what would you call this? A clever use of Hex of Weakness as intended, or an exploitation of a bug that classifies Rising Phoenix as healing? And, more generally, if a guild takes advantage of an odd mechanism in a fight that hasn't been classified as a bug by Blizzard, is it exploiting or just being smart?