In an effort to efficiently disseminate as much information as possible, many of these questions are amalgamations of several slight variations asked by the US, EU, Korean, and Chinese player bases. In addition, a few unanswered questions from "Ask CDev #1" are included as well. Enjoy!
Q: Are the Warcraft and World of Warcraft RPG books considered canon?
A: No. The RPG books were created to provide an engaging table-top role-playing experience, which sometimes required diverging from the established video game canon. Blizzard helped generate a great deal of the content within the RPG books, so there will be times when ideas from the RPG will make their way into the game and official lore, but you are much better off considering the RPG books non-canonical unless otherwise stated.
Q: Where is X? (X = Calia Menethil, Turalyon, Alleria Windrunner, Med'an, Gallywix, etc.)
A: There are several "missing" characters in the Warcraft universe, but they are not forgotten! While we'd love to talk about these characters, doing so would spoil a number of the plots we have for Cataclysm and beyond. Believe us when we say that you will definitely hear about these characters when we're ready to talk about them!
Q: Why isn't there a(n) X Archaeology branch? (X = Tauren, Aqir, Faceless One, Furbolg, Murloc, etc.)
A: This is more of a game design question than a CDev one, but it was asked enough that we wanted to at least point out the following: just because a race doesn't have an Archaeology branch now doesn't mean there aren't artifacts for that race, nor does it mean that the race isn't a candidate for possible future additions to the profession.
Q: Have we seen a true titan yet in World of Warcraft?
A: No, only their creations.
Q: Are night elves related to trolls in some way?
A: See issue #5 of the World of Warcraft Official Magazine!
Q: What is the relationship between the Ancients of the Emerald Dream and the loa?
A: Troll druids visiting the Moonglade have been overheard calling the wisps who reside there loa, just as they refer to Goldrinn, Aviana, and the other returned Ancients as loa. Night elves and tauren have tried to counsel these trolls on "correct" druidic nomenclature, but the trolls thus far have been stuck in their ways.
Q: If trolls are able to regenerate their limbs, why didn't Zul'jin's arm grow back?
A: For the most part, it is the speed at which trolls regenerate that makes them formidable foes. When in balance with the loa of their tribe, they are also able to regrow digits (fingers and toes). Tales abound in troll culture, however, of those blessed by the loa with extraordinary regenerative abilities, such as the ability to regrow limbs and even vital organs lost in battle. The tale of Vula'jin the Void speaks of how he regrew almost his entire body after standing in a pool of shadowflame. But just as the loa can bless, they can also curse; troll children are taught legends of those cursed by the loa, unable to heal even flesh wounds, to instill the proper respect for their patron spirits.
Q: What races were on Azeroth before the coming of the titans?
A: Besides the elementals, the only known sentient races on Azeroth when the titans' forces arrived to subdue the Old Gods were the trolls, the race known as "faceless ones," and the aqir. Due to the Old Gods' war against the titans, as well as the extensive terraforming that followed the war's conclusion, records of what races existed before even the Old Gods' arrival have likely been lost forever.
Q: What contact, if any, have the tol'vir in Uldum had with the rest of Azeroth over the course of their existence?
A: Although the systems keeping Uldum hidden from the rest of the world worked flawlessly from the ordering of Azeroth up until the Cataclysm, the tol'vir inside did have some knowledge of what was going on outside their home: many of the titans' security devices in Uldum were in communication with the other titanic cities (Ulduar, Uldaman, etc.). The Halls of Origination were actually the system that Algalon the Observer intended to activate upon his arrival in Ulduar… which the players prevented from automatically triggering when they sent the "Reply-Code Alpha" signal from Dalaran.