Removing CA w/ lens correction settings in LR did not solve the downsizing issue (although at full size it did look better, obviously). Out of curiousity, I decided to do some edits on the RAW file to make it look more how I would actually edit it, then went into photoshop and downsized. Same result. I thought maybe changing tonal qualities / contrast / color would have an effect on the edge artifact issue, but it did not. Final conclusion, when the issue arises, I will obliterate it with some of the techniques from my tests above. Thank you to all.