I had a lot of fun with a necro psycho back in the day with 1 socr for extra pet. I would like to do necro psyco again but what 3rd class would add the most passive damage if I am busy locking things down and cant take the time to ride?
Maybe try Onmyoji? An attribute for Fire Fox Shikigami will increase the range of Psychic Pressure, Double the hits of Gravity Pole and turn both skills into Fire Element making them benefit from Shoggoth’s Greater Corruption damage boost. Aside from that you only need to bother with Howling White Tiger (low cast time) and Yin Yang Harmony (a 3rd channeling skill!) among the other skills.