Is inside of Uldamann, in the Badlands.
If you have no need/desire to go into Uldamann, you can get someone to summon or portal you to Shattrath and get the same stuff from the Trainer in the Scryer's tier or head down to Hellfire Pennisula.
For Horde, you can find the Master Trainer at Thrallmar.
For Alliance, you can find the Master Trainer at Honor Hold.
