First of all, nice redesign attempt 
As someone who spend a fair bit of time on the device pages since I develop drivers I'd love to see improvements. Will we get any, probably not, but who knows?
In terms of needed information, since current state can contain basically whatever the developer of the driver want/need it to, it needs to be flexible in that aspect, here is an example of a button device:
Certain things in there, like the driver version, really belongs more under Device Details in Data, but then becomes hard to notice, putting it in Current State also puts it in the event timeline so that you can easily see when you changed version.
Without changes to how Current State, State Variables and Data works internally, the UI will probably have to live with the system as is, especially since a rewrite of all drivers would be needed if breaking changes were made. Not likely.
As you can see in the screenshot from @csteele, there can be a lot of information in Current States.
I understand your desire to rename "Current States" to "Sensor Status" for a sensor, unfortunately I'm not so sure that is a great idea. For one, there are plenty of switches which also have sensor capabilities.
"State Variables" also contain quite a bit of information and is often (ab)used to display information about the driver to users, like this:
but also very often used just to store data needed for the internal workings of the driver. I've added some CSS to some of my drivers which hides the stuff under State Variables and Data which is not needed by anyone to look at, this is not standard however.
The Preferences section of a driver can have a description set, which is not very often used, but I do find it helps users:
As for information and fields I use often is everything under "Device Information", especially the changing of driver under Type and renaming the device.
The Data section is one of those places that may contain a lot of information not needed by anything except the operation of the driver and for debugging if pairing of a device went as it should. For example, if endpointId is missing on a Zigbee device, expect most commands to not work as expected (depends on how the driver was implemented).
Talking about a new device page layout is fun, though I highly doubt we'll see one in the near future. For changes that only require CSS and HTML to be modified but doesn't change the underlying logic and structure, there might be some hope, for anything beyond that I wouldn't hold my breath unfortunately.
