This guy seems a bit tougher to get than most instanced nameds. I am breaking my 3 box up, each getting their own mission and seeing when he pops. Of course it is all random but I went 9 missions (3 chars getting 3 missions each) with no spawn. Then going another 6 or 9 missions before spawning him again.
He dropped Toriss' Chain Ring both times so guessing it is his common drop.
Edited, Jan 2nd 2010 10:38am by Boomsticker