The Vex Mythoclast is not just a toy to be bought from Xür.... It is a trophy earned from killing Atheon in Hard Vault of Glass. There is a reason to why Vex has a solar burn on a primary and Crux makes the arc burn Necrochasm. It don't matter if those weapons are irrelevant to other exotics like the Gjallarhorn or anything else. Those weapons are meant to be trophies that you have successfully defeated such big intimidating bosses... An luckily beaten the games more serious boss the "loot system"... Buying it from Xür is an absolute lazy solution... It's bad enough Xür sells the useful and powerful "Icebreaker".. It is an absolute horrible idea for him to sell the Mythoclast or Necrochasm... Personally I wish they made the Vex and Necro into bounties like the "Queenbreakers Bow, Lord of Wolves and Dregs Promise". I don't give one shit if you don't have those, people work there ass off in this game to get those and they have every right to rep them and use them.... Xür is a lazy solution to this game... It took me many many months to finally get my Vex, I still rep it here and there and I still remember when I got it and who I got it with... It is my trophy...