Fix Atonement please?

The healing effect of Atonement has a 15 yards range from the target that was DPSed. This wouldn't be a problem if it were 15 yards from the edge of the target - all melee would easily always be in range. But unfortunately it is 15 yards from the center of the target, making it basically non-functional on very large bosses or bosses that require the melee and tank to be at "max range".

So can you set the 15 yards to be from the edge of the hitbox? Or even just 10 yards from the edge of the hitbox would be enough. But 15 yards from the center of the boss is to often not enough.