It seems 
Decay Augmentation isn’t the only Witchcraft power getting disabled this weekend! As we’ve already covered, 
Twilight Warding has been causing a lot of player deaths, as damage could be reflected. This was a major issue in Hardcore, and Blizzard disabled the power until they can find a fix.
We have gone ahead and also disabled Twilight Warding as well this weekend. This was causing some weird interactions that could result in players (especially hardcore) dying unintentionally.
We have a fix being tested over the weekend and will roll that out next week once verified.