Awesome article. Diplo and I had some legendary fights on this board back in the day, but I always enjoyed reading his writings on various CV games. He picks up on things most folks wouldn't notice.
I think HoD is the best of the Castleroid games other than SoTN. I didn't like it at first, but once i started seeing it as its on thing rather than "SotN Jr" I really got into it. I love the music. I understand why people shit on it, but I think the compositions themselves are fantastic. It's actually one of my favorite OSTs in the series.
As you can see from Diplo's article, there are a lot of little touches in the game (like having to kill the monster to have its blood fill up the room so you can progress and things like that) that make the game a real labor of love.
I also really liked the A&B castles. Castle A seemed like what a CV castle should be but Castle B was a twisted, nightmarish version of it, much like Silent Hill's shadow or evil world. That's why I think this game is the best example of asset reuse in terms of level design.
The game has some rough edges to be sure, but I think that's one of the charming things about it. They shaved a lot of those edged off of Aria and I think it's to Aria's detriment in some ways. Still, HoD is a really great example of the Castleroid formula working well imo.