I wanted the monsters to feel embedded in their environment, like they know the area better than you, because you're just passing through.  Certainly they know how many of themselves are needed to stop you from continuing on.  This is what I'd call "emergent AI," or the AI that can be created by intrinsically tying a monster to its environment (instead of relying on coding in the monster itself).  Given that Heretic II is a fairly old game, I hope you'll notice my philosophy at work in this aspect of level design.
I did cut a few corners to move the story forward, lest everything would have taken months and months longer (I started this project, I think, in late 2005, and worked on it whenever I had time).  Also, my sister was getting weary of coming in for changes to the script, and the High Priestess plays such an important role that the story sort of pended on her.
Nonetheless, the game covers a scope as of yet unseen in any Heretic II Single Player release...it's what you might call an "unofficial sequel."
Have fun and enjoy the nostalgia!