Yeah, it really is that big of a deal. I remember when WoW used to do this, needing to carry that extra set of resist gear for certain fights. Then, there's always that one guy who left one piece in his bank accidentally and you have to wait on him to find it. Or the guy that somehow lost part of his set somewhere and has to go find it. Another set of gear that you had to gear a new member up in. I was also a Warlock and had to have yet another set of gear for a certain boss fight that you used a warlock in a specific set of gear to tank. Your warlock that has that set of gear not there that night? Well, guess we can't clear that boss that night. Blizzard stopped doing this for a reason so yeah, it is a big deal.