Where bugs are concerned, there is always going to be a priority system in game development. Visual bugs on a single piece of old gear are less important than something that allows you to kill a new boss ignoring all of the mechanics, or a bug that breaks a certain job's rotation.

It may be improved by the graphics update in 7.0 or its patches, which will be upscaling everything to 1080p and adjusting textures and shaders on armor. That may be why they aren't bothering yet, because it might be fixed by this much bigger update in the expansion or its patches.