Sadly, as long as raids remain isolated from quest progression outside of them, stuff like this is what we get; rather than tell us a story in the game itself, they plaster stuff on their web page so that they don't have to write the story into the actual raid.
It's extremely haphazard, and results in things like the unlikely-to-ever-be-updated encyclopedia on the official WoW site that they added to explain all the TBC stuff that they didn't feel like comprehensively explaining in-game. The resulting sense of detachment feels like watching a movie without sound and being expected to download a transcript at home and read it to get the character dialogue.
Secondary content should complement and enhance the actual game, not outright replace it.
"Reassembly is the reverse of disassembly"
"...except you swear in different places."
- Parody of Haynes repair manuals, original source unknown.
I've seen people complain that Bungie doesn't include enough material from the books in the games, as though they should be part of a single interlocking experience where the story arc weaves from medium to medium like a drunk driver slaloming along the Interstate.
—Well known admonishment to electronics users.
[Y]ou don't get credit for stuff you don't put in the movie because, now try to follow this because it's a pretty big leap, you didn't put it in the movie. I shouldn't have to wait months and watch all your deleted scenes to say "Oh, this finally makes sense," or pore through some non-canon books to say "Oh, so this isn't a pile of nonsensical horseshit after all." Sure, good films don't always tell you things on purpose, but that doesn't mean that a bad movie can get away with the same thing. Because while a good creator might say "I want them to ask what was in that box that drove him to do what he did," a bad one probably isn't saying "I want them to ask why is the villain doing something that even a coma patient would see as foolhardy, borderline insane, and actually likely to thwart his own plan?"
—SF Debris, reviewing "Star Trek: Generations"
The name of this world is Nalthis, by the way. Mistborn takes place on a world called Scadrial, and Elantris on a world known as Sel. See the fun things you learn by reading annotations?
"If you need instructions on how to get through the hotels, check out the enclosed instruction book!"