The issues with the whole block above the arrow-keys (INS, HOME, Page-Up/Down, DEL and END) not being properly bindable was reported in several threads during the beta. I aswell use them and basically rely on them. Since BF1942, btw.
Currently, in my fresh install i can't bind DEL, and while Page-Up is bindable, it's keypress seems to be ignored ingame.
It is really frustrating how such seemingly easy things, wich were working in BF3, keep getting **bleep**ed up, cause it's not the first time some keys are not useable.
Edit: thanks for the tip about BF4 Editor, I was able to get my layout to work. So the Probvlem clearly lies in the Settings-Frontend and not the game or engine in it self.