We're not "nerfing blindly." Keep in mind that, the debuff can be disabled. So if you and your Raid choose to do so, you can take on the encounter without it.
We also explained our thought processes in the original announcement blog about the debuff here
For those of you who raided in Firelands and/or Icecrown you're no doubt aware that as time goes on we want to keep people progressing by adjusting the difficulty. For any number of reasons a group may be having difficulty on a specific encounter each week, and our intent in adjusting the content is to ensure the ability to keep progressing, enjoying the content, and gearing up. With Icecrown we progressively buffed the players, and while this slow progression (and ability to opt-out of the buff) were both beneficial, it led to an expectation of your characters power, and once you left the raid you could certainly feel less effective. For Firelands we attempted to fix that by nerfing the content instead of buffing players, but we nerfed the content difficulty all at one time, which was counterproductive for players who really didn't need as severe a change as we made. With Dragon Soul we're attempting to do the best of both by having a progressive nerf to the content, keeping player power constant while providing small increases in assistance over a long period of time, as well as allowing players to opt-out of the assistance by speaking to Lord Afrasastrasz.
Despite arguments to the contrary, there is a choice involved here. You can choose to leave the debuff on or turn it off. If you're looking for the challenge that doing the raid gives you without the debuff and your raid group isn't interested in turning off the debuff, that is still a choice that is being made. No one is forcing that on anyone. If you personally feel forced, then it may be an option to find another group that is interested in the challenge of doing it without the debuff.
Meanwhile, the debuff affords those that want to progress a bit, who have experienced difficulty, more of a leg-up.
It's fine to disagree with us on this, but please make sure that you continue to do so in a constructive manner and refrain from starting flame wars or posting harassing/defamatory language toward posters in the thread.