Camped this room up the steps straight through the door from the Overlord for a couple hours one day killing the Water Elemental Overseer. You can actually get to the room with invis and preferred levitate, once you get to the first bridge drop off the side and straight down the hall make a right. Don't lose invis or you will probably add about 10 or so mobs. Very high roamer traffic in this area. Soloed Water Elemental Overseer with 80 beast real easy conned Green. He spawned back to back 4 or five times then a ph then spawned again 3 or 4 times in a row. Dropped the mask all but one time and the earring once with an uncut gem. Low aggro range, you can sit in the opposite corner of the room with no aggro.
This mob has a short respawn time around 13-15 min. The mask is the common drop and the earring drops around one out of ten. You can go five spawns without a named and sometimes you get two back to back.
It is a good place for xp if you can handle two mobs at a time and once I caught the Brigand, a fire elemental named, pathing through.