You get this quest once you kill Thunderaan, no one else can loot or even see the loot once you kill him only the one with the quest for the Thunderfury.

One very important thing, is to finish the conversation with Demitrian . Do not run off and spank Thunderaan the second he spawns, like some silly dwarf did, then have the raid group wondering why it never worked.

On the plus side, we got to kill him twice.

Still a great tanking weapon for AoE in my mind.

You get this quest once you kill Thunderaan, no one else can loot or even see the loot once you kill him only the one with the quest for the Thunderfury.Actually I remember helping someone kill him and I DID in fact see this item, of course it was master looter anyway. Perhaps I have a screenshot somewhere if I didn't delete it. (edit: after searching, and searching, re-searching, I was unable to find even one Thunderaan kill screenshot on this computer, however I trust what my eyes saw that moment)

Edit: Considering that the original poster posted this info almost 2 years and a half ago it was perhaps in the mean time changed to be able to be seen by others.
Edit 2: I have begun the Thunderfury questline today; when I am at this point of the questline I'll be able to confirm/deny what I said. (since I cannot find said screenshot)

It begins with Examine the Vessel, followed by Thunderaan the Windseeker, culminating with Rise, Thunderfury!.

The quest chain begins when you loot one half of the Bindings, which drop off Baron Geddon and Garr in Molten Core. Upon looting either of these, you must then travel to Silithus and speak with Highlord Demitrian. He will give you the Vessel of Rebirth, which begins the quest line.

The next quest requires you to present the following items to Demitrian:

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Both the left and the right Bindings of the Windseeker.
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Essence of the Firelord, which is a 100% drop from Ragnaros if you have the quest.
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10x Elementium Bar, obtained from smelting rare Molten Core and Blackwing Lair reagents.

Bring a raid with you when you return with the required items to Demitrian, because he will promptly summon Thunderaan, whom is not the least bit happy that he was locked away for so long. Defeating Thunderaan causes him to drop his blade, whereupon you can receive the Dormant Wind Kissed Blade. Deliver this to the now rather cowed Highlord, and he will make Thunderfury, Blessed Blade of the Windseeker for you.