This herb can be found in many places but we are going to talk about the place it is found the most.
Mainly Found in instances the herb can be a good money maker for you.
If your a rogue then you can just enter underbog and Stealth around without fighting mobs to be able to farm ancient lichen.
If your wanting to get dirty and nuke down some trash then head over to Mana Tombs and Aoe the lot down and do some cloth and gold farming at the same time also some good items drop from Mana Tombs including Cards and BOA equipment to sell or disenchant.
The spawn rate for this herb is very low and your not always going to find it when your farm a instances.