Long time lurker and first time poster here. I did a search and couldn't find anything on this certain spot.
This is a spot to grind Black Prince rep to honored for the first part of the legendary quest. It is located on the northern most island in Townlong Steppes at 35, 11 (Called Shan'ze Dao). Look for the beach on the north eastern side of the island.
There are Shan'ze Illusionists, who have 1.96m HP and Bronze Quilen which are in packs and have 78k HP each here that both give rep.
The best part is the Illusionists do a cast that is similar to mirror images that summons more adds that also give rep (10 each iirc).
The actual Illusionists give about 30 and the Quilen also give 10 if I remember (been awhile so these may be off). There are usually 7 of the illusionists and 3-4 packs of Quillen up at a time and they both have a fairly high respawn rate.
You can also drop a guild banner and gain rep even faster.
Link to imgur album here.
Hopefully this guide is helpful and posted in the right spot. Let me know if there are any issues with it!