Twilight Jasmine continues to be a top seller for the Herbalism profession in the World of Warcraft: Cataclysm expansion.
You can only find Twilight Jasmine in the Twilight Highlands, typically in "grassy" areas toward the center and upper areas of the map. While not inclusive to all spots that Twilight Jasmine grows in this zone, the red route outlined in the diagram should cover 75% of the nodes. Also note that the map includes an Elementium Ore route for Twilight Highlands, denoted in the blue color. About 1 in 15 Elementium Ore nodes will spawn as Pyrite ore, which fetches much more gold in the auction house.
The other herb that you will find commonly in Twilight Highlands is Cinderbloom. In the yellow shaded area on the diagram, there are multiple nodes. It is also dispersed throughout the zone in non-grassy areas, such as the purple fissures located in several locations along the Twilight Jasmine route. Even if Cinderbloom doesn't currently fetch the same amount of gold as Twilight Jasmine does at the auction house, it's still worth it to stop for them too, especially given that they produce Volatile Life at the same rate that Twilight Jasmine produces it.
The majority of nodes along the flight path do not have creatures to battle, though a few do. It will be difficult for players lower than level 81 to kill the mobs in these locations given that most monsters in the Twilight Highlands are level 84 or 85.
The big wild card in determining how much gold per hour you can make here is how many other players are also flying around and trying to gather these commodities. If you get lucky and get the zone with only a few other players farming, there are plenty of nodes to keep you busy. If it seems that you are fighting over every last node, you may want to consider heading to Vashj'ir or trying your luck with farming Embersilk cloth from some of the good humanoid concentrations in the zone. And, again as a refrain, having both Mining and Herbalism as professions is now viable (both can be tracked simultaneously), and will make any zone worthwhile to farm in. Until the roaring hot economy of early Cataclysm simmers, this is an easy means toward building a considerable amount of WoW gold.
Mount Hyjal Mining Route
Vashj'ir Mining Route
Deepholm Mining Route
Uldum Mining Route
Twilight Highlands Mining Route
Mount Hyjal Herbalism Route
Vashj'ir Azshara's Veil and Stormvine Route
Deepholm Heartblossom Route
Uldum Whiptail Route
Twilight Highlands Twilight Jasmine Route
Tol Barad Azshara's Veil and Whiptail Herbalism Route