This transmog reminds me a lot of the one I have on my Priest, except this one looks more suitable for a Frost Mage.
This is a very easy transmog to get, most of the pieces are BoA and available in a good quaintity on the AH. The robe and the staff are the only 2 items that are drops from a dungeon boss, I got them whilst leveling.
Shoulders – Arcane Pads (AH – BoE world drop)
Chest – Robes of the Exalted (Lord Aurius Rivendare)
Gloves – Arachnidian Gloves (AH – BoE world drop)
Belt – Arachnidian Belt (AH – BoE world drop)
Boots – Arachnidian Boots (AH – BoE world drop)
Weapon – Hydrocane (Viscous Fallout)