I play as a warlock and I'm generally lower lvl than most of my team mates (because I hate farming for materials and I have shit luck for gear) , yet in pve, I consistently have a better k/d, and a higher kill score - often double the body count of my party. In pvp, which I'm much worse at, I am generally in the middle range of my fire team... Skill dictates playability. If your friends have problems, it's because they aren't very good.