I recommend testing this by using 100,000 chaos scrolls on each type of equipment and see if the results match the intended probability.

Great question, and thanks for testing so many capes! We took chubby's suggestion and ran 100,000 Chaos Scrolls on your exact cape. Our results matched the reference server exactly. A Chaos Scroll re-rolls every stat the item already has by a random -5 to +5, all equally likely. It doesn't single out scrolled stats. With only +2 LUK, any roll of -2 or lower takes it to 0, which happens about 36% of the time, and LUK drops at all about 45% of the time. It also rises about 45% of the time. Your screenshot (LUK 2 to 1, W.DEF +4, M.DEF +2) is one normal result. So it's working as intended. Small stats like +2 are just the easiest to wipe out.