After the March 10, 2010, patch that changed the spawn location of a few rare/named mobs in Underfoot, I have had Eldaa Kemph spawn approximately at the following location three times in a row: -1035, +485, -217. (This is from /loc, not from the contents of the map file.)
This is in the small side-tunnel immediately south of the tunnel leading to the zone line of Pellucid Grotto. That tunnel and end-room is filled with traitorous dwarves.
Rondor