Hey.
The nature of Webdriver (the protocol Dalek is using to interact with its Browsers) forbids to access network stats & header access by design.
This is the fact, because the protocol designers want it clear that you should only simulate user interactions a "regular" page visitor could perform.
If you want to access the network stack, you have to use a proxy.
We have plans to include this functionality in future versions of Dalek directly, but this isn't an easy thing to do, if you keep in mind that
you have to support https & spdy. So it will take some time before we are able to ship it.
Cheers
Sebastian