For the /loc-challenged (like myself), use the left cave to nKal from Kal and go straight into the cavern that goes down. He is at the T-junction. As well, specwarcat was right (thhough not as clear as us dimwits would like). Diggins is a Rogue Guildmaster and findable as such...
Sometimes he stands outside the bank (to the right as you come out the door) at +604 +231 -33. Other times he stands at the bottom of the first ramp leading into the mines, at +658 +305 -53.