Straight from us.battle.net:
During the scheduled server maintenance on the week of January 31, the Dragon Soul raid will become enveloped by the Power of the Aspects spell, reducing the health and damage dealt of all enemies in the raid by 5%. This spell will grow progressively stronger over time to reduce the difficulty and make the encounters more accessible. The spell will affect both normal and Heroic difficulties, but it will not affect the Looking for Raid difficulty.
The spell can also be disabled by talking to Lord Afrasastrasz at the beginning of Dragon Soul, if a raid wishes to attempt the encounters without the aid of the Dragon Aspects. 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. We hope you continue to enjoy Dragon Soul, and that these changes encourage you to attempt a higher difficulty, or just keep pushing to down that next boss.
Looks like I might try reg DS late this year!