As for investigation while it sounds like a lot of fun it's tedious after the first few play-throughs, like any puzzle yes it's fun the first even second time but on the 10th it's more like hurry up and let me by, and if you haven't played the game in a while and forgot how to solve it, it can also be a pain. I think they have their place in games but dishonored strikes me and more action than puzzle and I just want to veg out and kill pixels.
Not that others won't enjoy a good puzzle.
Well, I'd agree that investigation can be tedious as hell after the first or second playthrough in any other game, but... This specific level served a lot of marketing purpose, with arguments that prove to be true like the randomization of the Boyle lady we are after. Both in term of name ( and by such how we can convince her to go somewhere she'd be alone ) and in term of dress color. The investigation here would have been randomized each time, which would have given a nice replay value relying on some refreshing mechanisms in a video game.
Instead they kind of half-did it, two characters who aren't even randomly placed in the level ( or at the very least I always found them in the same place ) will give you what you seek in a bit less than 2 minutes. 75% of mission done.
The art is still gorgeous in this mission, but it really feels... Short.