It's a farming extravaganza!
I managed to get all relevant characters to 85 to farm the holiday boss for the mount (or, in Dusty's case, the rose helm). This makes me happy.
An important change: you no longer queue from the LFD pane. You now have to go to Detective Snap Snagglebolt [H] or Inspector Snip Snagglebolt [A].
Previous years: 2010, 2009, 2008, 2007. 2010 has the achievement info you'll want.