Reported in game but for extra clarity here in the forums as well:
Healing from Atonement as Discipline Priest have two separate range calculations currently.
One for normal hits which calculates 15yd from the edge of hit box of your target.
One for Critical hits which calculates from the center of the hit box and causes trouble on fights with large hit boxes.
But it does have a significant effect on smaller hit boxes as well. This is easily tested on a target dummy if you are alone at 15yd so it barely hits you, you will notice that your crits will miss and wont hit until you scoot 1-2yd further forward.
There might as well be a issue with pets still having priority over players at times. If this is due to pets being the only targets in the smaller range or one of the atonement spells didn’t get the smart heal update from before I’m uncertain of, but should be clear from devs perspective.