nearly every game I know that has several pieces of armor usually has gear bonuses on the high ranking armor. So it only makes sense to me for the high end (raid/trials) gear sets should have some kind of bonus. Diversity was never about armor imo anyway, it was always about weapons. why the heck would I want a guardian that looks like a clown wearing all pieces of different stuff? Edit: they kind of did it with shaders (you needed a piece of each armor for EM and HM for a shader)