It is completely reasonable for people to have checked the appearance in the preview window and bought based on that. Since it's not common that gear changes appearance after it's in game, other than minor clipping issues, there's no reason most people would have ever considered checking for such a thing. Your attempt to throw all the blame on the players is ridiculous.
It's completely reasonable to check the Dev Tracker 5 mins during a day and make yourself aware of the known issues which may or may not affect you. In this case they stated a month ago it was wrong and would be fixed to match the promo art which also at that time they stated everything is intended to match the promo art. Not doing so negates any credibility to complain when they fix something that was incorrect to begin with and acknowledged to be.