Many Shadow Priests are not feeling very good about the state of the class in LK right now. Yes, buffs to DPS are promised. But a lot of our utility has tanked, from Shadow Weaving not affecting other players, to Vampiric Touch being dialed down and given to other classes, to Misery. It's sad, but amusing that a talent named Misery would get nerfed this hard.
Currently, in live, Misery gives 1/2/3/4/5% increased spell damage for all players against targets affected by your Shadow Word: Pain, Mind Flay, and Vampiric Touch. Pretty sweet. As of the latest beta version, it's +1/2/3% spell hit for all players against targets affected by the same spells. The reason this is especially bad (besides that the last two ranks of the talent were removed) is that most casters are hit-capped when they raid, which means that additional spell hit doesn't help them at all.
So either players are going to start gearing assuming Misery will be up – which defeats Blizzard's stated goal of making it so no class is truly essential for a raid – or Misery is going to be worthless most of the time (outside of leveling maybe). This seems like a good case of a broken talent, and so I have every hope that it will get addressed during the beta. But as of right now, Misery is pretty miserable indeed.