I just had this thought after almost 9 hours of hard mode raiding.
Let's say you have the best luck ever and every drop from the hard mode King's Fall is 320. From weapons to armor, their attack and defense values are 320. However we cannot reach the new max light of 320 because of our artifact.
The highest defense artifact we can get currently is from completing the Road to King's Fall quest at 310.
How are we supposed to climb the light ladder if no other place drops 310+ defense artifacts?