The Camelot Unchained site has been updated with some fantastic information about the latest class to be revealed, the Scout. Scouts come in three forms, each with its own set of unique abilities: Wisp, Specter and Arisen.
As an example, Wisps' background is that they can move undetected through enemy territory during the day and they're fast and hard to kill. Conversely, their slightly glowing bodies make them easy to see in darkness, hence less-effective.
You can read about each of the three forms on the Camelot Unchained site.