I've been thinking about this for a couple days now.
The fact that Nighthold takes place within Suramar City, and is in fact a part of the outside world, fighting those bosses really feels like you're going through the city sweeping up the big baddies.
On Krosus for example, you can see the Tomb across the sea, Dalaran is right above the boss – I can imagine people in the city freaking out when hearing his shouts echoing in the night.
Or people around Suramar seeing the top of the Palace getting ripped off, then huge explosions and a freaking tear in the sky.
I also really like the overall structure of the raid zone – the Aqueducts, where a couple 'miscellaneous' bad guys reside, that we just stumbled upon, and take out as we go. Then we enter the city area and take out generals, high-ranking guys, and once we secured that, we go after Elisande, who's alone aside from her ritual-casting members. Then even higher Gul'dan, right above this incredible concentrated ley-power line, a beefed-up Karazhan if you wish.
Going around exploring the different rooms and hidden areas is great too, there are lots of additional details scattered around.
Every night we go in I have a great time, Blizzard really outdid themselves.