Interestingly, I've never been able to get away with taking out that guard by the window. I've seen other people, like Mr Freeze, doing it on PS4, but unless I'm the unluckiest player on the planet then I always get spotted (on Xbox) by the two goons by the junk furniture near the house. It goes into instant Combat as soon as I subdue him. Also, I don't know if it was just behaving funny on the day, but I had to do my run three times because when I found that when I exited at the Tornado shelter before Diana says, "He is no longer our primary concern," then I lost my No Noticed Kills bonus. You seemed to just go through as soon as the exit appeared and preserved all your bonuses. I exited quickly the first time and I thought I must have messed up one of my kills. I couldn't see why, but I did my run again and the same thing happened. So the third time I paused at the exit before going through. It seemed to work. Strange?!?
And, yes, you were right. That Graves kill was brilliant!