Personally I believe this is something that needs to change and I'm going to ask SE about it the next chance I get. While it can be boring to see multiple classes or jobs all look the same when they have shared gear, what I consider to be even worse is when you decide to glamour the appearance something that is class or job specific. My current Summoner glamour uses the appearance of three job specific equipment and two that are not. Since my Black Mage shares gear it now looks like a total mishmash that isn't aesthetically pleasing. It's either live with that or don't glamour Summoner the way I want.