These goblins are found in Stormhold level 4 and 15 are needed for the quest "Cleansing the enemy" given by a skeleton in the upper level of Stormhold. (I'll add his name when I can remember it)
I ran all over the 4th level of stormhold and only found two of these suckers right at the hallway if entering from the jail. They're 27^^ heroic- 2 in the mob. I suppose you'll have to kill them 8 times, but they respawn fairly quickly. There's a couple named mobs on this level and I doubt many people go down there, so pony up for some fun.