While that makes a lot of sense, I believe the Gjallarhorn has a much lower drop rate, as I have seen repeats of every other exotic in the game, and not one Gjallarhorn, even at 1500 hours into the game. That cannot be simply a coincidence as guns such as the last word and icebreaker are extremely common, and I do not see anyone complaining about not having those guns, while the Gjallarhorn is many veteran players last exotic to strive for.