I fail to see how this is considered an exploit. Xur is currently the only vendor in the game who accepts strange coins as currency, and he sells different items each week. If you have three characters of the same class, there isn't much you can buy from him that can benefit you. The only item from Xur that isn't purchasable with strange coins is the Exotic helmet engram, which can only be bought with Motes of Light. And if the engram turns out to be an item that isn't suited for the three characters that you've made, it ought to be dismantled. The same can be said of the Weekly Nightfall. I have three Warlocks myself, and this week I've gotten Exotic armors that are only suitable for Titans and Hunters. Destiny isn't like other MMOs. There is no economy in this game. Players cannot trade items with one another but themselves; the gear is bound to the account. Furthermore, the vault has a limited space capacity, as you can only hold so much item in it. I enjoy collecting exotic and legendary weapons, but soon I'll run out of room to store them, and some of the guns will have to be dismantled for upgrade materials.