Sharpshooter
Midfield
Averages have nothing to do with it. Players are picked on form and dropped on a lack of it. Bancroft has scored 44 runs, Warner 18 - that's what I was getting at when I feel he can count himself unlucky. Does he deserve to remain on his current form? No, but he isn't the worst.
I understand what you're saying but that's as good as it gets from Bancroft. Warner can perform a lot better and its better the keep the potential match winner (as they haven't got many) than replace him with another opener who will battle to 20 before getting out.
England were in this situation with Cook for a long time because they didn't have any suitable replacements. It would make sense if they had Langer or Slater waiting in the wings but they don't.
Warner btw averaged 46 last time in England.