This is a Bluepost from Blizzard about the Justice Points you get from a lich king/Cataclysm Dungeon/boss and from lich king/Cataclysm Raid/Raid Bosses
Although we’ve revealed some details of the conversion process (https://forums.wow-europe.com/thread.html?topicId=14574620794&sid=1), many of you have asked how many Justice and Valor Points bosses and daily dungeons will actually award. This list is incomplete, and the values may still change, but it covers the majority of the content we’ve been asked about.
* Lich King Heroic dungeon boss — 16 Justice Points
* Lich King daily normal dungeon — 12 Justice Points
* Lich King daily Heroic dungeon — 23 Justice Points
* Lich King raid boss — 23 Justice Points
* Cataclysm Heroic dungeon boss — 75 Justice Points
* Cataclysm daily normal dungeon — 75 Justice Points
* Cataclysm daily Heroic dungeon — 75 Valor Points
* Cataclysm 10-player raid boss — 75 Valor Points
* Cataclysm 25-player raid boss — 105 Valor Points
It’s important to note that once you outgrow content, by leveling past it by a predetermined amount, you’ll no longer gain points. The ‘outgrown’ level for end-game Wrath of the Lich King content is likely to be level 81. Once you level beyond Lich King content you’ll still be able to enter the dungeons, kill bosses, and see their drops, but they will not award you with points. This same principle applies to all content that provides Justice Points, including content from The Burning Crusade.