They aren't ruining anything. Black Hammer is by far the best sniper rifle in the game because it gives you completely unlimited ammo with a fairly quick fire rate and absolutely no wait/reload, assuming you're a good sniper. It is ridiculously broken and despite absolutely loving the gun, I feel it does need some balancing. Gjallarhorn is and always has been mean to be a fantastic super nuke for PvE. The problem is that a ton of players are being excluded from end game activities for not having one, which Bungie has a problem with (as should any reasonable, caring individual). They haven't even explained to what degree it's being nerfed. You have two options from here: Continue being a closed-minded, selfish crybaby and quit now, or chill the eff out and wait to see what actually happens.