Noticed this last night and just now. After killing the trigger mob (Guardian of Doomfire) to start the Fennin Ro event, it spawns two copies of every mob along the path to FR. I'm not sure if this continues beyond this point after the first round of mobs as I haven't gotten that far.
Last night while pulling him it also somehow agroed every mob in the rectangular area before him including mobs with no line of site. Didn't have that issue today so that may have just been some one off weirdness.
Thanks!