Cleansing Drak'Tharon

1. Loot 5 Enduring Mojo off the trolls that come after the raptor boss.
2. After killing final boss, go down the steps behind him and use Drakuru's Elixir at the brazier there.

If your partymate has summoned Drakuru and you attempt to use the elixir at the brazier while Drakuru is around, your mojos will be consumed without anything happening.

But don't worry! Just stick around and wait for Drakuru to finish his RP scene. Even if you didn't get to follow the "summon Drakuru" part in the quest instructions, you can talk to him and turn in the quest after his 3-minute RP.

if you're making your way through the instance and are wondering where all the enduring mojo is, they only drop from the last stretch of trash mobs before the final boss, the trolls that are fighting each other.

I had a hard time finding this thing. I thought it was the one that the NPC was in at the time he gave you the quest way back at the beginning, not so. The one you need looks similar but is a bit larger. You can find it just past the last boss as you go down the stairs to take the "water elevator" back to the other quest givers.
Also, the "?" on the map here is wrong. It's on the "Overlook" floor, that part is right, but it's way over to the left, NOT in the center of the platform. It also is NOT on the other floor (the Vestibule)
Hope that helps somebody.... I submitted a screen shot as well.