Well you see not everyone has started playing Destiny yet, many will likely start on the release of TTK, that being said Gjally shouldn't be OP, no gun should

Bungies logic does yet doesn't make sense. They are introducing sleeper simulant, which any player can get with a bit of dedication, and has equal or out damages Gjallarhorn per shot, with more ammo. They just sold it, so discriminations out of the picture, if you seriously can't get 17 strange coins together, I'm not sure you should be raiding or doing end game content in the first place. However, they are saying that bosses in the taken King will focus on having raid like mechanics with less health, so I'm assuming that they will no longer be insta killed by Gjallarhorn. I feel like they shall carry out the nerf to make the Vanguard Ursa strikes a little harder, along with pre-Ttk strikes.

The getting kicked was just one symptom of the issue. They were basically saying that it was so OP, that it was creating and artificial requirement. Giving everyone one, while treating that symptom, didn't resolve the underlying issue. It's like taking a Tylenol for a head ache, but not getting the knife sticking out of you head taken care of. The nerf is fixing the OP. Giving one to everyone would just treat the headache.

Their philosophy is "if you choose one weapon for EVERY encounter you enter, we need to make some changes. There shouldn't be any one weapon that is the best in every situation."