I finished Rocksbourg 3, but I'll be honest when I say that half that mission scared the living hell out of me. I think that was the intention, though. DrK loaded that mission with sounds and atmosphere that sucked me into the thief world so much that I couldn't help but be frightened by a few of the "surprises" that I won't list here. I think alot of the reason I really enjoyed the "somewhat undead" souls of Ink and Dust were due to the setting being different than your average 'yeap, another cave or abandoned church'. It was totally new, totally fresh and had an amazing backstory.
Oh, and invincible monsters are one of the most frightening things you could ever put into a thief FM![]()
As for Mission X - I put it in my post for one of the best missions of the year simply because of it being a technical achievement of the likes that I've never seen before in a thief fan mission - everything about it (especially after the latest patch) was completely polished and well designed.
That being said - it just wasn't my kind of FM. I think the extreme difficulty pre-patch really turned me off - Not to mention that my first couple playthroughs were attempted without knowing you could lockpick light switches in some areas.
I'm probably in the minority when I say that I'd take "Pirates Ahoy" or "Broken Triad" over Mission X simply because the gameplay style I enjoy is more simple and Original Mission-like than most. But again, Mission X was incredible and I'm sure you'll enjoy it.
Edit: I just played the German language mission that you had mentioned - Definitely not for me. Poorly designed identical corridors in a maze full of hammer haunts.I think I'll pass on finishing that one.