There are some admittedly ridiculous damage parses that show shadow priests doing massive damage (to bosses, rather than giant enemy crabs). While Mind Blast is probably hitting too hard, the real issue is that we synergize too well with warlocks' Dark Intent, resulting in those extraordinary parses. When we don't have access to a warlock, our DPS is more ordinary.
We do need to have one of our spells tuned down; it's the price we pay for being able to heal at all...but this change is befuddling.
Konoka, I agree Shadow Priests benefit greatly not only from Dark Intent, but from Bloodlust and Time Warp as well.
If Shadow Priests gain more benefit from those abilities over other classes, then indeed, changes should be made. I don't necessarily agree with how Blizzard is making that change. However, if the change is due solely based on class ability synergism, then that is an unbalanced change.
Further, if Shadow Priests are producing more DPS overall compared to other classes when the above mentioned abilities are not a factor, then the proposed change begins to make sense.
On a side note, yes Blizzard gets a hug from me. Who doesn't like a hug now and then? =)