you can only get 1 weapon per week. it changes each week

Well people like you are very lucky they buffed the drop rates depending on how many times you kill the boss on the same instance. Because it took me 41 Clears to FINALLY get a drop and it was the SMG. On my 57th Clear I got the Shotty and on my 61st clear I got the Sniper yesterday. You better hope your RNG is better than mine because I suffered through horrendous RNG. Some people get really lucky, I saw a guy with only 2 clears and he already had the Shotty. Here's a tip. Make sure to use the Exotic Ghost shell to better loot drops from Public Events and use Fire Team Medallion every time you do EP. It helps.