Stonetalon

When I arrived in Stonetalon Mountains via Ashenvale, it was clear things had changed. At the entrance there you do some quests for the Horde which are fighting the Alliance in Windshear Craig. On your arrival you are given a rank roughly equal to a PFC (Private First Class). As you quest through Stonetalon Mountains you gain rank, which allows you access to better rewards from the quartermaster located at Grom'gar Fortress (also located in Stonetalon Mountains).

After finishing a flurry of quests in Windshear Craig, you are sent to defend Malaka'jin. As you ride through you will notice that the Grimtotems have been defeated, which is part of a phase as later you will be fighting them again.

After defeating Malaka'jin, you are sent to Windshear Hold for a few quests. You then take a hot air balloon which is carrying a huge bomb to the Sludgewerks for another quest or two before finally coming to Cliffwalker Post. Cliffwalker Post is where the Stonetalon story culminates before the rank you have been working on is stripped from you and made worthless by the Warchief. (You still have it for getting things from the quartermaster though)

I won't spoil the story for you, but make sure you don't miss it and include this on your tour of Stonetalon! Stonetalon lasted me until roughly level 28 where I had a choice to go to Desolace or Southern Barrens. When I went to Desolace it had changed somewhat, but still had the gloomy, boring atmosphere as before so I decided to go to Southern Barrens.

Pictures left out for spoiler sake.