But there are many, many lighting conditions above complete darkness where the outline of a threat can be seen and night sights work well. And of course, tactics have to be driven by the situation. If we know the only person we're going to run into is the threat, and he's a dangerous threat then that may be all the threat ID we need. E.g. in my house, if I know my wife is beside me and there's another person in the house, the third person is a threat. I don't need more ID than his outline, although in all reality I will have a light and likely a laser on him.
I do like the DayGlo approach, that may be a better choice in most situations than night sights. Of course that would mean the threat would have to have some artifical light on him if it were dark, but nothing wrong with that!
And since I've already given myself away, my real tool for low level is rapidly becoming a light/laser combo. Because of the laser, you don't have to have the gun at eye level or even next to you. Same for the light, yet you identify and acquire the threat without having to bring the gun in line with your eye/head.