Jade Forest serves as the starting zone and the literal impetus, in terms of story, for what drives you to the rest of Pandaria. Without the events of Jade Forest, the rest of the zones simply would not happen. In fact, without the events in Jade Forest, I suspect the rest of Pandaria would have been largely uneventful. The key lies in our arrival, which is a shift in the direction of the storytelling. We aren't reacting to traumatic events anymore; we're the cause of them.
But it's the endgame that has changed so significantly that it's unlike anything we've ever seen before -- and it's changed for the better.