Securing Draenor

For those curious, you CAN use the missives sold by your Garrison vendor for 200 Garrison resources each to get this achievement.

The only one that won't be sold is the quest for the Pit, because it is a group quest.

Assault on the Iron Siegeworks: Assault on the Iron Siegeworks[H] Assault on the Iron Siegeworks[A]
Assault on the Magnarok: Assault on Magnarok[H] Assault on Magnarok[A]
Assault on the Everbloom Wilds: Assault on the Everbloom Wilds[H] Assault on the Everbloom Wilds[A]
Challenge at the Ring of Blood: Challenge at the Ring of Blood[H] Challenge at the Ring of Blood[A]
Assault on Mok'gol Watchpost: Assault on Mok'gol Watchpost[H] Assault on Mok'gol Watchpost[A]
Assault on Darktide Roost: Assault on Darktide Roost[H] Assault on Darktide Roost[A]
Assault on Skettis: Assault on Skettis[H] Assault on Skettis[A]
Assault on Stonefury Cliffs: Assault on Stonefury Cliffs[H] Assault on Stonefury Cliffs[A]
Assault on the Pit: Assault on the Pit[H] Assault on the Pit[A]
Assault on the Broken Precipice: Assault on the Broken Precipice[H] Assault on the Broken Precipice[A]
Assault on Shattrath Harbor: Assault on Shattrath Harbor[H] Assault on Shattrath Harbor[A]
Assault on Socrethar's Rise: Assault on Socrethar's Rise[H] Assault on Socrethar's Rise[A]
Assault on Pillars of Fate: Assault on Pillars of Fate[H] Assault on Pillars of Fate[A]

If you are Horde, you should know the Apexis daily Challenge at the Ring of Blood needed for this achievement is currently bugged and is never offered to Horde players.

I have been advised by a GM to wait for Patch 6.1 and see if it is fixed then. Please submit an in-game Bug Report for this known issue.