The time it takes? It's random, lol. You could get one the first time you run a strike, or a year into the game.
I've put more time into this game than probably 90% of this forum, and just recently got a Hawkmoon. I knew HM being capable of one shotting people was bullshit, fun as it may be, so to be shocked, or outraged at it getting nerfed is silly. The same applies to a RL that could melt boss encounters in a minute, completely bypassing the mechanics of the fight.
As I said yesterday in the Destiny community thread, saying Gajllerhorn is needed to combat bullet sponge bosses has no merit moving forward, because I don't believe they will repeat the same mistakes of those strikes. So to leave the weapon as it is for the new content could have made it even more broken than it already is. You have to look at the broader picture of this update, it isn't even hitting until TTK, and these changes have been made with that game's balance in mind.
The knee jerk reactions without even seeing how it will truly play in the next content is stupid.
Does someone have a gun to your head making you play this content over and over that you don't seem to have fun with?
The game needed a weapon balance patch badly, the loadouts have been stale for quite a while. The game will continue to get patched and balanced, there will always be an evolving meta, and if you have a problem with that, then you're going to spend a lot of time mad at the game.