I have just done this quest and can confirm that the mugwort is at the coordinates that Jolaren has stated 2.4N, 39.0W; 2.2N, 39.0W; 2.3N, 39.2W, and 2.4N, 39.3W
I just finished this quest and the new location of the Spiky Mugwort is just west of Tascgall's location at: 2.4N, 39.0W; 2.2N, 39.0W; 2.3N, 39.2W, and 2.4N, 39.3W