Here's a bit of proof that you don't need to be incredibly skilled to kick some ass in Uncharted 3's multi-player. Today, I played a Plunder game. All the members, except for one, had Legacied at least once. It was a heated and competitive match that was going back and forth, and I wasn't goal tending, as people tend to do in Plunder. I should add that the Villians team was made up of a four man Party that was using voice chat.
I'm not an incredibly skilled player in online games. In Call of Duty MW and Black Ops, I get whooped, most of the time. Still, I managed to have a 34 to 9 Kill to Death, and 16 Assists in this Plunder match. I've even won some Free for All matches.