I know that healers are not supposed to have a rotation, and they shouldn't, but this time they went to the other extreme: Atonement is very weak, not only it's nerfed in numbers it's also extremely unreliable since half of the time it heals people on 98% health, and this is not hot ticks, most of the major heals were penance and holy fire instants.
I honestly think they didn't do a good job with disc this time around. Someone had the forced thought that "Atonement is too easy" but he didn't think it through:
He didn't think it through because if it works as it works, if you give 99% HP people your major heals, atonement is useless or extremely unreliable.