There are actually only 4 trains per hour between 9pm and 11pm. The extra trains that you include involve trains to Norwood Junction and then returning in the opposite direction (which takes longer than waiting for the next direct train).

I am still very annoyed about the unneccesary removal of the evening Charing Cross services and I do not see how the East London Line will benefit people returning from the West End in the evenings. People will end up changing at Waterloo to the Jubilee line and then having to take the London Bridge/Canada Water gamble. How much better it would be to run services straight through from Charing Cross and Waterloo East, as is done today.