As I commented below, I have 3 full sets of VoG raid gear and I couldn't careless if they are obsolete. I will be using all faction gear to get to 31 even though I already have some raid gear. It's worth it to not be using an exotic until I can upgrade it for Xur. Plus at 31 you stand a much better chance defeating Crota. He certainly isn't going to laugh at you because you're wearing mismatched faction gear. So I'll gladly hit 31 tonight wearing 0 exotics and 0 of my old raid gear.