The encounter journal is an amazingly thorough description of every normal and hard mode encounter, with lists of abilities and in many cases instructions on how to deal with them. It's fully functional on the PTR - which means that any top raiding guild has access to everything it needs to know to defeat Heroic Ragnaros, right now.
Some of the more melodramatic top 10 EU guilds have already expressed their opinion on this being the Cataclysmic End to Raiding in the World of Warcraft. Since it's too late to take this information back, Blizzard has made a very clear statement:
Discovery and inventiveness in raiding are bad, with perfect execution being all that matters.
As someone who's been raiding at a higher level than most of you can ever hope to achieve, I have to say that I'm a bit saddened (though not shocked) by this slide. The days of creativity are slowly drifting away, replaced by those that can field the most technically perfect raid and nothing else.
The world top guilds will remain world top guilds, but the progression race for this tier has been irrevocably ruined.