Just to confirm what others have said, I got this sucker to spawn four times in as many hours at the aforementioned area just past the frogs. Mauk spawned in three locations: twice at the first static before entering the three-way room just around the corner, and once each at the two statics in that room (these can also spawn Felsa, too). This is in addition to the spawn points by the catapults near RCC, so that's at least five different PHes.
Just west of the ent to the korascian caves is a gobby soldier ( or scout ) A static spawn. I was killing him and got this named to pop twice in only about 5 kills. Maybe I was just lucky, but he seems more likely to spawn here.
Exceedingly rare, have camped him for a total of about 15 hours and seen him zero times. I was killing the gob ph near the catapult closest to the fire as well as the goblin (scout, soldier, skirmisher) near the fodder goblin models. I do not believe the fodder ones can spawn him so I did not kill those.
I have killed him 3 times at loc 1391.41 312.67 this is at the 3 way intersection headed to the Rathe zone. I started killing all goblins and mobs near that to see if he would spawn anywhere else there. no luck yet
His /loc is p2898 n678 next to a catapult. It's right by Catapult Morg operator. The mob was a lvl87 Rogue when I fought it. It being a rogue, his DPS was pretty decent. If you can handle other named in this zone though you shouldn't have a problem. Sorry for a lack of details, but I was busy. :)