I decided to go here on my lvl 17 with a friend. The respawn rate seemed to be determined by the amount of players in the area. when it was just me and him the spawn took 5 minutes. when another 2 people came its timer was around 3m. I haven't had a respawn timer faster then 3 minutes for this guy.
EDIT: forgot to add that i can confirm he drops a soul gem every time.