Wrath of the Lich King: Moreso than Burning Crusade, arguably. Tauren and Dwarves both uncover long lost ancient relatives. Forsaken faction schism, large scale forsaken military movement against the Lich King. Small bit of Gnome lore. Reasonable bit of Blood Elf lore (via Sunreavers, Quel'delar). Minor Night Elf lore (failed world tree). 0 Draenei lore (what the fuck else is new?). Major human lore. Little Orc lore. Little Troll lore (not the right kind of trolls, at least).