Hey, the energy circle is a nice additional tool, but it doesn't means pilots have to stop thinking...
You can make up a very good estimate, while being radar vectored, you can say you need XXX track miles to touch down, just by looking at the display.
Whatever the case may be, I like to keep 300 feet per mile for my own calculations, so I know it fits the picture (i.e. 3NM final= 900', etc)
Flex