The dot on the bgwiki map is pretty accurate (Duke Scox should be A-6 too though):
http://wiki.bluegartr.com/bg/File:Dynamis-Xarcabard-NMs.gif
There's a NIN and SAM combo on one side of the demon steps and a DRG,DRK,SomethingElse on the other side. There's another NIN a little farther to the west that's more difficult to pull.
I spent one run killing the NIN that's coupled with the SAM and didn't see the NIN NM pop, though I popped all three of the others (SAM, DRK, DRG). I went again and killed that same NIN PH most of the time and again I managed to pop all three of the others without the NIN popping. Finally, I started pulling the one farther in (I was on BST so it wasn't bad) and I managed to pop Marquis Gamygyn off of that one.
I don't know if they're both placeholders and I just had bad luck but the one farther in is definitely a PH.