To get the item, you'll have to finish the ""pyramid"" event in Zul'Farrak, it envolves waves of trolls elite and non-elite, you'll have the following NPCS help you...

You do NOT need to PvP flag for the NPC to heal you. I know this from personal experience.

NPCs in order of priority

Oro Eyegouge, Orc Warlock : https://vanillawowdb.com/?npc=7606 https://vanillawowdb.com/?npc=7606
He is usually the first NPC to die. If you protect him he will continue to cast rain of fire and put DOTs on incoming trolls. He is an aggro magnet. Melee attacks disrupt his rain of fire and seriously reduce his dps. If you keep him aggro free, the trolls die quickly and your odds improve greatly. Toward the end of each wave he will run out of mana, and jump into melee combat.

Murta Grimgut, Dwarf Priest : https://vanillawowdb.com/?npc=7608 https://vanillawowdb.com/?npc=7608
She is the only NPC who heals, making her very important. Mostly she struggles to keep the rogue NPC alive. But she will also shield or heal you, if she has the mana. Healing causes her to draw aggro from every loose mob running up the stairs. She is more robust than the warlock, presumably because she can shield herself. When she runs out of mana she will jump into melee. If you keep her alive, the rogue's odds improve as well.

Raven, Human Rogue : https://vanillawowdb.com/?npc=7605 https://vanillawowdb.com/?npc=7605
She stands in the front row and takes a severe beating. But she deals lots of damage and is important to protect. If the warlock and priest are free of mobs, go help the rogue.

Weegli Blastfuse, Goblin Engineer : https://vanillawowdb.com/?npc=7607 https://vanillawowdb.com/?npc=7607
This guy is surprisingly tough. He deals area damage using land mines and bombs. This brings him aggro, but he can usually handle it. Unless you wipe, the goblin will most likely survive. Which is fortunate because he is needed afterward, to blast a nearby gate to get towards the end boss.

Sergeant Bly, Human Warrior : https://vanillawowdb.com/?npc=7604 https://vanillawowdb.com/?npc=7604
He is a very durable warrior, able to look out for himself.

(Goblin and Bligh are equally important, Bligh for the questline and the Goblin opens the gate for the last boss, make sure they both stay alive - they are your main priority at max while this event happens)

After completing the event you can pick a fight with Bligh. This allows you to kill Bligh for the quest, remember, talk to the goblin for him to open the gate, DO IT FIRST (he once ran off while we were fighting Bligh). Behind that gate is another boss who minds his own business until you are ready. If you don't have a quest involving Bligh, you can just ignore him and ask the goblin to blast the gates.

EDIT: - [patch 3.03] It's possible the NPCs do not take damage anymore since this patch, I've ran this instance 6 times today, and everytime none of them have been injured, coincidence or fact? - can anyone clarify?

Get to the Large temple in Zul'Farrak climb up the stairs, up there is the Sandfury Executioner, he can be cut down easily loot the key from him, release the prisoners.

Sudenly a great mass of non-elite trolls will askend below the temple and will charge in waves the Trolls are 43-46 and give no loot. Kill the first wave, more will come a bit stronger than the first (still non-elite), when you kill that wave to get ready for the third and final, wich contains some elite trolls. Once you have killed them of. The former prisoners will get down from the temple till the Altar below.

Before you do anything heal and get you mana up again. then the Tank must talk to seargent Bly. He and his troops exept the goblin will charge you. The Dwarf heals from time to time, so kill her emidiatly after Bly.
When they are dead loot from Bly the Divino-Matic-Rod and continue the instance.

Well, I just tried it and it seems after...ooh...going on 4 years, they've finally fixed the HS bug that let you fight Bly on his own.

Such a shame, really.