Has anyone figured out how to identify the unique page of each separate Safari Web Content process with Safari 7/Mavericks?

If you hover you mouse over the name of the Process a Tooltip will show up telling you the URL Base domain

This is not an ideal solution but a quite good working workaround.

Open Safari then go to Preferences. Activate the Debug option (Show develop menu in menu bar)

EDIT: Instead of activating the develop menu, you have to open a terminal and activate the debug menu with defaults write com.apple.Safari IncludeInternalDebugMenu -bool true

Thanks @Collin C.

You will find the option Show Web Process IDs in Page Titles under Debug > Miscellaneous Flags

If you open the Activity Monitor now, you can see the Web Process IDs to the corresponding websites.

I hope this is helping you.