Little late to the party, but about the Reavers, its a pretty significant reference if you read the books/short stories. Its the first reference in TW2 to Geralt's relationship to Yennefer (one of the Reavers called her Connifer or some such). The Reavers are in the short story, "Limit of Possibility," which is heavily referenced later in the game. I don't want to spoil it too much but just know that you (Geralt) was a friend of a Golden Dragon (which was also referenced in TW1).
I wouldn't call the Reavers in the short story background characters. They and their leader, Boholt really caused a lot of trouble for Geralt and Yennefer. Theres also kinda a major story and game spoiler related to the Golden Dragon I don't want to ruin.