This has been an issue for about a year now. People who don't get dungeons or whatever that they want so they leave new players who queue for their dungeons normally. What's worse it's usually the tank or healer too.

For example, I got into a Brayflox's Longstop this morning sans a tank and was the in progress healer. The tank left instantly when he saw it was Brayflox and apparently was a mentor. PLEASE DO SOMETHING ABOUT THIS.