The four Scenarios are "Blood in the Snow," in which you assist with the defense of the dwarven capital; "Dark Heart of Pandaria," a cleanup mission in the Vale of Eternal Blossoms; "Secrets of Ragefire," in which you help the Gob Squad track a kidnapper; and "Battle on the High Seas" (screenshot above), a naval battle between the Horde and Alliance.
World of Warcraft's new Heroic mode is a tougher difficulty setting that's available for the aforementioned Scenarios and for "Crypt of Forgotten Kings" and "A Brewing Storm." Queuing for Heroic mode requires an item level of 480, and a few hardy friends. It's a stiff challenge, but the rewards are alluring: you'll receive Valor Points and will have the chance to discover Raid Finder-quality items.
Blizzard said last month that patch 5.3 will also introduce a new feature called Loot Specialization. The studio hasn't yet announced a release date for patch 5.3; patch 5.2, "The Thunder King," went live in early March.