I was glad that Shandor was in it and that they expanded on his backstory, but yeah I was a little disappointed. I've always thought of Gozer as the Ghostbusters ultimate adversary, especially in the movie universe. The idea that he's for some reason now doing the bidding (seemingly) of a guy who used to worship him didn't really sit well with me.
A lot with Gozer and Shandor somewhat confused me in this. I may have misunderstood, but didn't Shandor say that he set up the Mandala for Gozer, but decided to use it himself when the Ghostbusters beat him a second time? But since Gozer was going after Dr. Selwyn, it seems to imply that Shandor was already seeking to take the Destructor Form for himself before that second defeat. (*peter)