Farming Volatile Air in Twilight Highlands
The best place to farm for Volatile Air is from the Storm Vortexs at The Twilight Breach in Twilight Highlands. The Twilight Breach is just north of Victor's Point and just south of The Gullet. Here you will find Storm Vortexs all over the "sundered" landscape. They can most commonly be found alone just on the outside of the pillar of purple light around the center of the area but you can also find them walking with a Twilight escort all around the grassy areas surrounding The Twilight Breach. Unlike the Volatile Earth farming area I recommend killing the Storm Vortex's you see being escorted by the Twilight mobs.
The reasoning for this is because the Storm Vortex's only have roughly 50k HP making them extremely easy to burn down and since the Twilight mobs are casters you shouldn't have a problem blowing them up either. There are about 5 or 6 Storm Vortexs that spawn alone and another 5 of 6 that spawn being escorted by Twilight mobs. They are on a fast respawn timer so even with other people here questing or farming you shouldn't have too much trouble finding something to kill.
Volatile Air Farming Video: