MMO-Champion has a bunch of data from the Beta build, which I think means that the Legion Beta has either started or will very soon.
So far, there are a ton of details of questionable value. It looks like the artifact acquisition quests will likely be solo scenarios. Of note, the Ashbringer one seems to be an attempt to rescue Tirion Fordring, which might contradict predictions of his demise, though we could of course fail to do so (and then need to seek, say it with me... Retribution.)
The biggest thing I've seen is the surprising location of Dalaran above Deadwind Pass. Dalaran will certainly also be in the Broken Isles, but the maps seem to imply that at some point or another, we might see Dalaran above Karazhan.
Obviously, more info to come. (*Crosses fingers for a beta invite.*)
There are some boss descriptions in there. It looks like the Drogbar like to use horrible monsters to fight their enemies. Neltharion (aka Deathwing) was clearly corrupted by the Old Gods, and I wouldn't be surprised if some of that Old God/Faceless corruption had a presence in Neltharion's Lair. Additionally, it looks like the Violet Hold is currently just filled with Scourge - there's a Blood Princess, a prototype Festergut/Rotface-style abomination, and a Crypt Lord. And it looks like these ones aren't being held back by Bolvar.
More updates as they become available.
There are also a lot of things that appear to be quests or scenarios related to getting your artifact weapons. The one that stuck out for me seems to be for Marksmanship Hunters as the way to get the Windrunner Bow. This apparently takes you to another world, Niskara, home to the "Legion Inquisition." I'd guess this is the world or one of the worlds where Turalyon and Alleria have been. We know that there are new demons called Inquisitors, but I don't really have any idea what the Legion Inquisition does.
There appears to be a new hunter pet family: "Mech" which presumably will be the category that Gnome Hunters' starting pet will be. Given that my Dwarf Hunter is a Gnomish Engineer and clearly gets along famously with his Dun Morogh cousins, I really hope there's a way for non-Gnomes to get one of these pets.
How did I miss this? Looks like Millificent Manastorm, Milhouse's wife, is one of the bosses of the new Violet Hold. While described as a complete opposite of her husband, the two do have a tendency to wind up in magical prisons for incredibly dangerous beings.
Two entries on the dungeon boss list that should look familiar: Ymiron, the Fallen King, and Cordana Felsong. The former you should recognize as the king of the Vrykul who A. ordered all the pygmy children (aka humans) killed and B. pledged his people to the Lich King. So yeah, this guy seems like the ideal Vrykul to send to Helheim, and I suspect he's the first boss. (Also, I think the Helheim dungeon is going to be called Maw of Souls.)
Cordana Felsong might seem puzzling if you haven't completed the Legendary Ring quest. Well... um... Spoiler Alert, I guess. Over the course of the quest, Cordana takes a shadowy orb - a Burning Legion device of some sort - in order to destroy it. She doesn't seem to get around to that, and I'd guess that the orb wound up corrupting her, because at the end of the quest chain (well, except for the "defeat Archimonde" part) she goes evil, using the power of the Tomes of Chaos you collected to empower herself and try to kill you. She escapes, and I'd bet that she's the one who helped Gul'dan infiltrate the Vault of the Wardens, making it likely she's a boss there.
We're now getting the names of some class champions:
Death Knight: Thassarian/Koltira Deathweaver (these are grouped together. I don't know if that means that they come as a team or if you only get one or the other,) Highlord Darion Mograine
Demon Hunter: Lady S'theno <Coliskar Captain> and Kayn Sunfury <Illidari> (the former is presumably a Naga, which is cool.)
Hunter: Emmarel Shadewarden <Unseen Path>
Mage: The Great Akazamzarak, Mog'dorg the Wizened
Monk: Li Li Stormstout, Chen Stormstout
Rogue: Lilian Voss, Vanessa VanCleef... WHAAAA???? (I guess if anyone could fake her death, it'd be Vanessa.)
Warlock: Lulubelle Fizzlebang and Ritssyn Flamescowl, both <Council of the Black Harvest>. (Hope Lulubelle is a better summoner than Wilfred. Ritssyn is mentioned, I believe, in the Green Fire chain, and might be a Worgen?
Warrior: Commander Lynore Windstryke/Nazgrel (I'm thinking this might be either/or depending on your faction,) and Eitrigg (who for some reason I thought was a Shaman.)
Anyway, definitely some cool stuff. Definitely a mix of established characters and new ones. Very curious to hear about how VanCleef survived.
More Class Champions! Also, there are several blurbs about the champions that describe their backstories. Notably, Vanessa VanCleef totally faked her death in the Deadmines.
Lord Maxwell Tyrosus appears to be a Paladin champion as well as Lady Liadrin (though she was the first class champion revealed, so no surprise there.) Aponi Brightmane will be a Paladin Champion as well, along with Vindicator Boros, a Draenei from the Hand of Argus (get us a Dwarf and we should be covered!)
Altrius the Sufferer (who you might remember from Nagrand (Outland,)) will be there as well, presumably as a Demon Hunter champion. Someone named Allari the Souleater looks like a possible Demon Hunter champion, though her description almost implies that she's leaning more toward Warlocks.
Additionally, there's Zeros, who seems to be a dragon whelp and Mage Champion.