So, before the patch, I had 6 points invested in the passive damage increaser on my artifact ("Fleshsearer"), but as of 7.2 it has been stripped down to just one point. Do I get an artifact power refund for those 5 wasted points or not?
When you unlock the new traits, you will receive back any Artifact Power you'd previously spent on rank 36 onward. You can then spend this on the new traits.
One of the first new traits you can pick-up will provide you with the full bonus that rank 54 previously gave. This means that if you didn't reached rank 54 before, you'll actually end up with a stronger weapon than what you came into the patch with, once you get this new trait.