Tanaan Diplomat

This is one of the achievements for the upcoming 'Draenor Pathfinder' meta, required to unlock flying in Draenor! Take special note that this achievement only requires revered reputation and not exalted.

To fully complete the Draenor Pathfinder meta-achievement, you will need to complete: Draenor Explorer, Master Treasure Hunter, Loremaster of Draenor (A) or Loremaster of Draenor (H), and either Securing Draenor (A) or Securing Draenor (H). You will also need to attain revered reputation with [faction=1849], [faction=1850] and either [faction=1847] (A) or [faction=1848] (H) depending on your character's faction for Tanaan Diplomat (A) or Tanaan Diplomat (H).

There is also mention of a rylak mount, [item=128706] as an additional reward. The ability to fly will apply to all of your 90+ characters after any one of them possesses all the prerequisites (So, no need to grind reputation on every alt that needs to fly), however it will not appear in 6.2.0 but rather in a later minor patch (referred to as 6.2.x). Note that Draenor Pathfinder is account-wide, it has been confirmed that you won't have to 'earn' all of the achievements on the same character but merely possess them on said character.

Quote from the Dev Watercooler on Flying:

In an upcoming Public Test Realm build, we will be introducing a new meta-achievement called Draenor Pathfinder. You’ll earn this achievement in Patch 6.2 by mastering the outdoor environment of Draenor—exploring Draenor’s zones, collecting 100 treasures in Draenor, completing the Draenor Loremaster and Securing Draenor achievements, and raising the three new Tanaan Jungle reputations to Revered. Initially, this achievement will award a rylak mount: the Soaring Skyterror, one of the native beasts that roam Draenor’s skies. Players will remain ground-bound on Draenor until a small follow-up patch (6.2.x), when all players who have earned Draenor Pathfinder on at least one character will unlock the ability to fly in Draenor on all their level 90+ characters.

Draenor Pathfinder is account-wide progress, meaning each sub-achievement can be done on different characters. But it looks like Tanaan Diplomat must be done on the same character as the data does not indicate this particular one is account-wide. Another example is a Glory of the X Raider meta--you can have different meta-achievements across characters, but you can't split completion of a specific boss achievement between characters.

Do yourself a favour and get a Level 3 Trading Post for the 20% reputation bonus. I just got the Pathfinder achievement and found the Order of the Awakened faction to be a pretty awful grind. The only way to get rep is the faction daily for the Fel Corrupted Crystals. You have to kill rares and/or loot treasures.

You will quickly run out of Tanaan treasures without killing rares. And competing with the opposite faction on a PvP server will present additional challenges.