Just now cracking this link open.
I notice that the Corpse Marrionate is missing from the excerpt from Dungeon Delve. (Edit: No, wait, it's in the area features. Hahha, minion bomb.)
But, holy CRAP the Bonemaster is a nasty solo guy. He slows anyone in his aura, and can spam "Daze and Immobilize" every round. Not to mention pop minions into being. (What's cool is that he does Radiant and Necrotic to enemies; makes sense why he spanked the vampires in the first place).
I do like the adventure expanding suggestions, although the suggested secondary dungeon (Hag, chuuls, etc) sounds really crowded. My 'those monsters are odd, living together in such a little space, below a vampire crypt' sense is tingling.