Both Alliance and Horde players can participate in Secrets of Ragefire. Like other dual-faction scenarios, you'll be transformed to fit the situation -- in this case, everyone gets to be goblins as you assist the Gob Squad in their mission. Heads up though -- you'll want to keep the various members of the Gob Squad alive as you progress through the scenario. If you do, you'll get an achievement out of the deal.
The mission starts out with a pretty straightforward task -- blow open a door. The Gob Squad will do the dirty work of setting up the explosives, all you have to do is pull the trigger once the bomb is set. Stay back out of the way and watch it when those doors bust open -- there's a lot to see, but there's also a rampaging group of very angry orcs on the other side that aren't exactly happy to see you. The mobs in here aren't too terrible, although there are some shaman that drop some pretty nasty totems -- knock over the totems if you can, they either stun or pack a punch.
Once you've completed that task, it's time for your first "boss" of the scenario, a dark shaman named Xorenth. He's not happy to see you. In fact, nobody down there is happy to see you. You've just busted in on some particularly sensitive and top-secret information, and Xorenth is there to make sure you don't get out of there alive with that information. He's one of the more difficult fights in the new scenario -- you can't just push him over.
Since Xorenth is a shaman, it means you're going to have totems to deal with. The nastiest totem he has in his arsenal is a frost totem that will stun anyone within range of it, leaving Xorenth free to wail on you as much as he'd like. You can try destroying the totem, but it's easier to just kite Xortenth away from them by interrupting his casts. The other thing you'll want to watch for is Xorenth's massive ground attack -- you'll see rubble piling up on the floor. Don't stand in it, run out of it, let him finish his casting and then resume wailing on him. It hits harder than you'd think.
Once Xorenth's dead, it's time to do some investigation and see what, exactly, our Warchief has been up to down there in Ragefire Chasm.
It's not good news. You'll need to check out three different areas of the cavern, handily marked with a gear icon. Once you've uncovered all the info you need, one of the Gob Squad will try to blow open a door so you can escape. Unfortunately, she's going to need some ingredients to craft a bomb with that kind of blasting power. Fortunately, those ingredients happen to be sitting around the cavern, waiting to be picked up.
I wouldn't suggest picking up those items solo unless you happen to be packing some good raid gear. When you grab each item, a different pack of mobs will spawn. Lava spiders aren't that difficult to handle. Proto drakes will blast jets of fire at whoever happens to be nearby -- if you're taking them on solo, they can pack a punch. The last mobs are casters that will hit the ground with an AoE attack -- step out of the AoE and resume punching until they've fallen over.
Once you've got all the ingredients, the bomb is set to go off! Except that the door is way too strong, and the knockback from the blast did two pretty terrible things -- first, it hurt most of your Gob Squad allies. Second and more importantly, it just alerted a giant group of very cranky orcs to your presence. Uh-oh! Fortunately the Gob Squad has a teleporter that can get you out of there -- but you're going to have to fight off a few throngs of angry mobs while they set it up.
The groups will jump down from the upper ledges as shown in the screenshot above. There's the usual assortment of casters along with one very large and very angry Kor'kron Dire Soldier. While the smaller mobs are pretty much the same as the ones you fight at the beginning of the scenario, those Dire Soldiers have a stacking debuff that causes them to do 10% more damage with every hit. In other words, you want to kill them very, very quickly.
Once you've defeated a few groups, Overseer Elago will hop down to confront you himself. He casts an AoE on the ground that stays put. Just kite him in circles around the room and whatever you do, don't stand in the AoE. Once he's dead, the teleporter is functional and you can head on out -- your mission is done! Pat yourself on the back and head on out.
Secrets of Ragefire isn't a particularly complex scenario -- the mission is really straightforward. It's the story behind it that's interesting. What's Garrosh up to? What else has he got hidden in the heart of Ragefire -- or does he have more secrets hidden elsewhere around the world? And what's all that nonsense about Dragonmaw and proto-drakes about, anyway? These are all things we're going to have to wait and see to find out -- but I suspect we'll see them all addressed in time -- or in patch 5.4.