We used a different tactic. And the sniper don't need to take out all the nights, just the 2 nearest to the team and have the other 2 nights at half health because they don't shoot and will respawn with full health if killed. The ogres spawn on the second round and that's when everyone should go to the bottom room all the way to the back. Snipers to the back and guys with rockets to the front. Weapons of light is a bonus. When the ogres are down return to the room opposite of where crota is standing and clear the mob of thrawls and nights quickly. Then rinse and repeat. Have a look at my gameplay video. I was the main sniper.