Found him today, hit him with root and snare no other gobbies aggroed.Slapped him with Winged death ,Breath of Ro and Drifting Death.He went down and dropped earring, yay.
After killing this mob 3 times and seeing the Wretched Earring of Pain drop all 3 times, I think it's safe to conclude that this is his common drop.
His placeholder is always a goblin miner. The mob is located at about -2100, -1250, inside a small cave that branches off to the south of a much larger cave. In this smaller cave are 4 mobs. The goblin miner is the second one from the left when facing the four mobs. Thre is also a wandering mob that comes into this room. All of these goblins, including Miner Gribok, seem to be lower than level 45. I think they are closer to about level 40, possibly even 38, although I couldn't tell for sure.