Look at 00:16 secs. There it shows the buffs that the priest had. As you can see, there are only raid buffs, not timeless buffs. Moreover if you watch carefully, you can see how the hp bar of the hunter in the party decrease way too fast, and that's suspicious. But the thing that is wrong is the amount of shadowy apparitions, and how suddenly all the other surrounding hordes, which the shadowy apparitions attack once, are dead.
In this case, it doesn't matter if it's a damage hack, an exploit or whatever. The priest is using something to kill Timeless Bosses in an easier way, and should get punished with his/her guild for taking advantage of this.
