The "a harpy explorer" mobs that spawn on highborn island in the caves are NOT the one's you are looking for to complete hunter. They are NOT even the PH. The PH is any of the wandering harpy's on the prev island and he will have the first letter capitalized in his name.
The ones that spawn at static locations range from 63-66ish have never dropped anything for me but common vendor loot.
However the lower level one always seem to be 59-61ish spawn randomly anywhere (seen on 4th isle the most) drops the Harpy Slave Vambraces. Has all 6 times I have killed him in the last 3 days.
I've been camping here for days for experience, split between 2 characters. These con DB to my 68 Ranger, and Red to my 61 Cleric. My guess is that these are level 65, not 60 as is posted here.
There are 4 static harpy explorer spawns at the far end of the caves in Harpy Mesa (4th Island, Captain Island, according to your lights).
One is by herself on a ledge, 2 are in the last big room, and one is in a large dead end room by herself. All are single pulls with plenty of room to kite except the ledge spawn. There is one Harpy Highborn that paths in this general area, but can easily be avoided or taken out.
I have killed this cycle (along with the lone Blackfeather spawn on last ledge) several times, perhaps 16 kills total and have never seen the wristguard or Vambraces drop. The only time I got an armor drop was on a wandering explorer on the Third Island. May be a coincidence, not really enough data yet
after spending 2 plus hrs trying to get a violent to pop with no luck this was the only odd name harpy up so took a peek at alla and it only lists the 2 plate drops yet we got nada...=-/
I zoned into Blackfeather right after the patch today and saw two of these up. Both of them dropped a harpy pinion feather and an amber but no wrists or arms. Coincidence?