I was worried that this zone would be for lack of a better word too "Hellish" I am happy that after seeing the screenshots they did it in a way that gives the player the understanding that they are in the domain of fire, but not in this endless pool of flames and surround by lava. This was the same thing I was afraid of in Northrend that we would just have snow everywhere, but they got around that there so I should have had the same confidence they would have done it here. So I must say I am quite impressed with the screens and the look of the zone.
In addition with some data mining they have gotten 3 partial achieve icons. One of which is no surprise at all and that has to do with Ragnaros. The other two are interesting. One being with Fandral Staghelm, which is very interesting in the fact that he was transported to "safety" during the mount Hjyal questline. Even more interesting is that he was corrupted by the Old Gods specifically the Nightmare and her is hoping they bring this more to the forefront. Also I think a real druid type encounter would be quite an interesting one. Lastly is Alysra, who is the green dragon that helped you transport Fandral. Now this could either mean she is some how corrupted or gone rogue or could be Dreamwalker type encounter when she is required to be saved.
So even if we have to wait a little longer for the Firelands seeing the screenshots and this boss revelation makes me understand this will be an interesting zone and raid for sure.