Now I know what you're thinking, "but I see him in the Hunter's Dream!". That's actually why I think he is dead in reality. To enter the Nightmare of Mensis, you must come into contact with the mummified remains of a Mensis scholar (likely Micolas cage). If it is Micolash or any surviving member of the school, then it is possible for your physical body to die, but your spirit enter the dream realms of the Great Ones. So, what if the body in the abandoned old workshop is Gehrman? When you loot said body, you get the One Third Umbilical Cord, a tool that CAN be used to commune with Great Ones. It would then explain Gehrman's connection to the Moon Presence. Just something I was thinking about today in the Hunter's Dream.