I agree 100% it is extremely lucky, and nothing more than that. I hate the people who think any of their weapons are "earned." The only exotic you can say you actually earned is the Vex, and that's only because it's the only exotic (besides Nechro) that you need to accomplish a certain goal for a chance to receive it. I did Atheon probably 30 times before it finally dropped, and i will say i earned that weapon lol. But i do play mostly all PvE only, so i run both raids 3x a week and do Nightfalls as well, so i get a good amount of chances for exotic drops