Atonement was changed in BfA to not include procs in its healing. (e.g trinket direct damage and azorite damage traits)
Currently in the simulation script for Atonement, there is a section allowing for any spell hit to trigger the atonement.
It has led to the best in bags suggesting damage trinkets and damage based azerite traits that actually dont increase your healing.
They changed the wording of the spell in 8.0.1 to reflect this:
Old - When you deal spell damage, you instantly heal all targets affected by Atonement for 40.0% of the damage done.
New - Your spell damage heals all targets affected by Atonement for 60% of the damage done.