I'm making this topic as a followup so some
discussion in the bug report thread because I don't want to derail that.
I did in fact get another Vampire Castle mission, and although I didn't run into anything near the same issues as before it was still more trouble to finish than it was worth.
I've attached the save for the last part of the mission, dubbed Operation Let's Melee Cheese The Shit Out Of These Zombies Since Melee Is Really Hard To Train And It's Not Like I Can Make Synthsuits Or Anything Because I Never Get Any Mutons It's Just Sectoids Every Single Time Ugh.
(It does use the 30-turn bug hunt mod as well as a custom submod I made, the latter of which just sets the female frequencies to 50. It doesn't affect the mission at all.)
The last time I was here mentioned I couldn't access a large chunk of the map, but this time around that was not the case. I had the dining hall behind the gate that time, not the crypt block that's there now. I could swear that the parallel passage that connects to the other two rear blocks wasn't there, though I'm not ruling out idiocy on my part.
I didn't have to camp anywhere near as much as before because I had flying armor and once you get familiar with the map moving into the castle is not so bad. Nevertheless, I hung way back for the first part of the mission because of that bloody vampire queen. That thing is just way too dangerous to get close to. It can fry your soldiers at range just by thinking at them. So, since it always hovers around near the walls I just sent my tank after it (which it nearly broke anyway) and relied on long range aimed fire. After that, the tank took out any Strixes it could find because those can ruin your day if you let them, and following that the fliers got down to the business of hacking apart zombies.
So the state of the mission as it stands in that save is that there is ONE enemy that appears entirely unreachable. It's stuck in the underground on level 0 all the way on the east side. A second enemy apparently jumped into a grave near the player start, or downright spawned in it. Killing it is easy enough, but suffice to say I would never have found it without Bug Hunt mode.
At this point I debug killed those last enemies because I didn't have the will to tunnel down, or pull everyone back.
So, overall thoughts.
I think I'm not a fan of the gates. They're kind of annoying to remove because standard grenades won't do it and hitting them with projectiles can be tricky. Maybe they should be solid objects that can be seen through, like the glass walls on some maps.
Ultimately though, I think it all comes back to the queen. Not only is it by far the most dangerous thing on the map, it's also the MacGuffin you're there for in the first place. So far so good, but you encounter it almost right away. Then once you deal with it you face a choice of either killing the rest enemies or going in to collect the queen's body. The first choice can be problematic, as demonstrated by my save. Moreover it feels like a chore because the objective has already been achieved. The second choice can ALSO be problematic because the queen often hovers over terrain you can't get to, so if it happened to fall on such a tile you might as well just abort.
In summary the issue with this mission in my opinion is that it near enough opens with a boss fight, and then follows up with a long and frustrating bug hunt that is potentially unwinnable. Oh, and having to climb out of a hole in the ground at the start is kinda mean.