This game works on weakest link in the chain. One time i was doing a nightfall, phogoth, and i was using a sniper rifle and two shoting every knight. I was level 31, my friend joined as a 28, and suddenly it was taking 3 shots, the first two leaving knights with about 5-10% health. So if you're raiding with 5 32's, and one 29, he's bringing everyone down substantially. That being said though, I'll run VoG with any level as long as they can start the mission at all, and crota. Just requires some focus fire