It's the easiest fix to the real problem which is aoe damage. There is much angst among some melee players about kill count in quests and this should help level the playing field.
It's possible that ruin and greater ruin aren't impacted by this as it's untyped damage rather than normal magical damage, although not sure how to test it since the math isn't in the combat log.
The better way to fix it would be to scale down aoe spells a bit while leaving untouched (or even boosting a bit) single-target spells. This is just a far easier way to address the issue.