Avengers of Hyjal

It turns out that Marvel superheroes are helping us defeat Ragnaros.

The Firelands Dailies give Guardians of Hyjal rep.

Avengers rep is only available by killing NPCs in the Firelands raid instance.

Also, similar to the way rep worked in Molten Core, most trash will only give you rep up to 5999/6000 (1 point away from Honored)

After that the only creatures that give rep are [npc=53115]s, [npc=53134]s and Bosses.

Edit: the more difficult trash beyond Shannox's/Beth's areas also gives rep past honored at the same amount as the hounds and giants.

Starting with 4.3 Guild Standards are again usable in Firelands. Duration has been increased to 15 minutes, the effect has a 100 yard radius, and now affects dead players.

That means you'll be able to farm reputation faster once 4.3 goes live.