I copied Sthenno over to the test realms yesterday just before they went down for the next patch because I wanted to see if the healing from Atonement was affected by Grace or Archangel. The answers were no and no, as I expected. What I didn't expect is that Atonement does not heal for 120% of the Smite damage as advertised, but rather for 12%.
I'm not really sure what to think about this. When they changed it to 120% I thought they were a little crazy, since this makes its healing coefficient per second well over double that of Heal's and with the mana return from Archangel means that Smite will replace Heal for discipline priests with about 4.5k spell power or more - that is, all discipline priests. At 12% I can't fathom how those points would ever be worth spending. With a factor of 10 it should be easy to tell which one is the bug and which one is intended, but to be honest I just don't know.