To check for backlight bleed you need to put a plane black image on the screen (completely black and in full screen), then turn off any other lights. If there is bleed you will see areas that are visibly lighter than the rest of the screen. SOME bleed is expected on all monitors (especially IPS), but it shouldn't be bad or obviously visible in normal light. It should be faint and quite even (so e.g. if 1 corner is clearly brighter than the rest of the screen, avoid).
Dead pixels appear as a bright or dark spot. Usually it takes a number of "dark spots" for you to be able to RMA the monitor, but less (1 in Asus' case) bright ones. Dark spots off center on a 1440 or 4k are not really noticable.
Another issue the Swift has is pixel inversion artifacts, which appear as vertical stripes on moving images. But it seems to be related to the out of the box colour, brightness and contrast calibration. If you adjust them down some it almost goes away.