GoW demands a tactical approach, or your average runner/gunner will be considered fast food for the Locusts. You'll need to plot out strategies and take cover, even if you wind up creating that cover yourself. Need somewhere to hide? Surely there's something nearby you can blow up, leaving behind chunks large enough to crouch behind. Of course, you could also try having your teammates fire blindly so that frightened enemies will be less inclined to emerge from their hiding spots making them highly grenade-able.