World of Warcraft Heart of Flame legendary staff quest chain?

I'm on the quest right now collecting cinders, i will be on essences in about 7 more weeks. How time consuming this is is driving me crazy by the time i get the staff it will be useless, now on the Heart of Flame quest i have to Smouldering Essences from a dead boss, but its not a loot item it appears to be taken from an already looted boss (kind of like skinning is done to something already looted). My question is if i can find group to do this can i just go in after every boss and siphon the Smouldering Essence from the dead boss and leave without being saved to the bosses and knock out all 250 essences out in a week?