Any build can farm Mandragors in Lahtenda Bog from Blacktide Den just circling the area between the Res shrine and the first intersection. This circle has numerous Mandragor pop-up groups, (including a boss in the ruins to the right). Run time is under 6 minutes, with usually 0-2 roots per run.
Mehtani Keys is a great place to farm them. Three groups will pop-up in the land area close to the rez shrine. I used a SF Assassin to ball them up and tank them and then a RoJ Monk to nuke them. Only takes 3 mins and you get 0-4 roots per run. Can also keep going past the "formation" in the middle of the water for another group. Kill/run past the group of plants to the left of that group for one more group.
Go to the water-side cave in Panjiang Peninsula just outside Tsumei Village to farm the Naga. Considering their level in Normal Mode just bringing any type of AoE/PBAoE damage along with a self-heal will allow you to farm the hides needed in just a few minutes.