Have took this guy down 5 times last week while farming in Drangonscale. He spawned for me on the hill next to dungore 4 times and once next to the farm. Easy solo kill with the mage doees summon but doesnt have many hp's Rampaging Servant eats him in a couple casts. So far one set of pauldrons and 4 chilform chokers ... hope this helps .. take care.
High hit was 1070, but didnt stick around too long.
Immune to run speed changes:
[Tue Nov 13 22:12:05 2007] King Mustef tries to bash YOU, but misses! [Tue Nov 13 22:12:06 2007] You regain your concentration and continue your casting. [Tue Nov 13 22:12:06 2007] Your target is immune to changes in its run speed.