Yes they do. There is only 2 places to farm them and they are extremely camped usually.
Orsis in Uldum and a small area east of Grim Batol in Twilight Highlands. In Uldum the mobs respawn at a decent rate, but they are like 200yds apart so it takes a while to farm them and its easy for people to tag mobs from you.
Twilight Highlands has a much lower drop rate, but the mobs are closer together.
Air's a pain to get. it's the only Volatile i don't have like 1000 of.