I agree with fistofice on the spawns, but I believe it may not have been mentioned that there are specific locations for these goblins, rather than mixed in with all the rest. Since I'd never hunted pick claws I wasn't KoS, and wandered around looking for the spawn points. I also found three of them - starting from the first floor with pick claws (a fairly big landing with a large prominent wooden pillar in the centre) there is a spawn in the back, beside the hole in the wall, that spawns this type. In the side room immediately off the landing, with two spawns in the back and one immediately beside the door on the opposite wall - the single is this type. Lastly, there is a single goblin in the elbow hallway in the very basement, just outside the raider room - that one also spawns this type.
Wiped these three mobs three times, and found a scroll on my fourth clear. Spawn time is 10M+, and all three of these points I listed had 'a goblin', 'a crazed goblin', and 'a goblin thief'. Got my drop off 'a goblin', but according to other posters, all of them will drop.
Last pertinent article of information is that every other type of goblin has 'pick claw' in their name.