This is the official Diablous transmog since patch 4.3

Head: Zeherah's Dragonskull Crown
Sold in Orgrimmar by Jamus'Vaz and in Stormwind City by Faldren Tillsdale.

Shoulders: Craterflame Spaulders
Drops from Alysrazor in Firelands10/25(H), or if you are shaman, can be bought with Shoulders of the Fiery Protector, which drops in Firelands10/25(H) from Majordomo Staghelm. Sold in Orgrimmar by Gunra and in Stormwind City by Magatha Silverton.

Belt: Titan-Forged Waistguard of Salvation
Sold by Stone Guard Mukar(Horde) Knight Dameron(Alliance) in Wintergrasp.

Chest: Chestguard of the Lasher
Drops from Freya in Ulduar10(N).

Weapons: Blackhorn Bludgeon
Horde only! Drops from Anub'arak in Trial of the Crusader10(N/H), or rewarded from quest Regroup!(also horde only item).

Gloves: Trapper Gloves
Northrend world drop. Same model as Orca Fists, Skom Gloves and Garmaul Fists. BOE, so it's easier just to buy from AH.

Legs: Inferno Forged Leggings
Sold in Shattrath City by G'eras.

Boots: Greaves of Withering Despair
Drops from High Interrogator Gerstahn in Blackrock Depths aka BRD.

Tabard: Tyrannical Gladiator's Tabard
No longer obtainable.
Weapon Enchant: Bloody Dancing Steel

Flying mount: Furious Gladiator's Frost Wyrm
No longer obtainable.

Ground mount: Dark War Talbuk
Sold in Nagrand by Coreiel(Horde) and Aldraan(Alliance). Costs 100 Halaa Battle Token and 20 Halaa Research Token.

*NEW* Ground mount: Midnight
Drops from Attumen the Huntsman.

*NEW* Illusion: Glorious Tyranny
No longer obtainable.

Macro for Mounting:

/use [flyable, nomounted, button:1] Furious Gladiator's Frost Wyrm
/use [noflyable, nomounted, button:1] Dark War Talbuk
/dismount [mod:Ctrl, mounted]
/script EjectPassengerFromSeat (1);
/script EjectPassengerFromSeat (2);

Macro for Tmorph:

.race 2
.item 1 77150
.item 3 71556
.item 4 89195
.item 5 45941
.item 6 46074
.item 7 30772
.item 8 22240
.item 10 36230
.item 16 47905
.item 17 47905
.item 19 98162
.spell 127663 113656