Blizzard is nerfing Priest Mind Soothe today! RIP Halls of Infusion Routes.
The most common use of Mind Soothe in Season 2 dungeons is to skip the trash gauntlet between the 2nd and 3rd boss in Halls of Infusion. If you wish to skip this it will not be much much harder or be a death skip most likely.
You can find out more about why nerfing Shadow Priest damage isn't as important in this article by Ellipsis.