Gjallarhorn is not that strong... It is balanced with other launchers fairly well... It's just a favorable weapon for bosses because the wolfpack rounds go to the enemy you shot the rocket at... Hunger of Crota does nearly as much damage only its secondary rounds drop to the ground not always doing the same damage with the secondary... Truth doesn't do as much damage but it has a massive blast radius compared to others... Each of the weapons (specifically exotics) are situational weapons, meaning there is a time and place for all of them... Hell even No Land Beyond has become one of my preferred exotics for Roc Strikes now that I've learned how to use it properly. All the weapons are used in preference or in the situation it calls for that weapon. Regardless of if Xur sells it which he should eventually so everybody can have the option to use it, its not going to hurt or hinder any other players. When you start a Crota fight and you are the swordbearer your only wish is that everybody have a good tracking rocket... if everybody can get a Gjallarhorn wouldn't it make the game better? The more people with more a variety of weapons the better. Everybody should have a weapon for every situation so your Fireteams can work better together. If you don't want the Gjallarhorn to be sold your too caught up in your own ego to see how it would make the game better...