As Chris said, that information has been removed from the latest version of the diagnostics too; presumably to stop people freaking out about it. It will still tell you the rate of discharge, which is *significantly* lower than it would have been previously.
The full charge capacity was fluid like that since the update before this one, it's nothing new, and definitely nothing to worry about. It will fall as the day goes on and rise as you charge it again. For your own piece of mind it might be best to uninstall the old diagnostics tool and get the new version.
I would say that my battery comfortably lasts 2 days with light to normal use, mostly on WiFi; which is not triple what it used to be, maybe not even double, but definitely a marked improvement.