Above and beyond that, it also ruins the experimentation that might make Blizzard say "Yeah that's a nice way to do it too".
Did Blizzard intend for the adds on Anshal's platform to be kited? What about Magmaw's parasites. If we had the neat DJ that said "Parasites should be quickly killed" then you are essentially forced into the strategy, since if that strategy isn't the norm Blizzard will have their hand forced to change the fight to make it so.
While the wording on the Rhyolith entry might be a little bit too detailed I still don't see how it explicitly tells you how to do the encounter.
I don't see how this changes a whole lot from an experiment stand point at all. The encounters were never black/white before when we knew of data mined abilities, and it won't be now. I think people aren't giving Blizzard enough credit in thinking that with this journal, there will now only be one way to do things.
They only fix things that entirely break the spirit of the encounter. They likely do design encounters to be completed a certain way but as always leave room for them to be done in different ways. Some ways are obviously not intended and outside of things that are pretty much exploits they usually let them stand.
We ARE still as players going to find interesting and unique ways (or strategies they didn't account for) of defeating encounters. This is largely because there are far more of us playing the game, compared to designers designing this raid content. It has and always will be there right to decide whether or not we push the boundaries of completing an encounter in a fair way.
They could have guided people through ICC with the dungeon journal for such bosses like Lady Deathwhisper. Specifically telling you things like:
*HEROIC* Insignificance: This reduces the tanks total threat generated by 20% for 1 minute. It stacks! You better swap tanks or else your DPS is going to get themselves killed. Oh yeah, the boss is untauntable.
*HEROIC* Adds: On heroic difficulty 3 adds will continue to spawn on alternating sides, in addition to one coming from the stairs! You better deal with these quickly before you get overwhelmed.
I tried to use some of the lingo that Blizzard has been using in some of their dungeon journal entries. Most people would infer that you would want 2 tanks swapping aggro on Deathwhisper and one tank picking up the adds. People would obviously watch their threat and keep the adds down as to not be overwhelmed.
What is STILL going to set guilds apart are things like this. This fight was considered difficult (comparatively) when first released but it didn't stop guilds like Premo from having a Warrior kite EVERY single add around with piercing howl, thus eliminating an entire aspect of P2. Same goes with the insignificance. Of course threat was removed when you got mind controlled, but it obviously wasn't intended that you could simply sit there with MD/ToTT and have a single tank literally tank the entire phase.
What makes you think Blizzard is going to abandon this approach. Regardless of what abilities are known and how 'on paper' blizzard designs the encounter to be played out there are going to be a lot of ways to beat these boss encounters.