I usually play with one other person and if someone does this we sit down until the random finishes the strike or leaves. If they do up to the boss we'll keep killing ourselves until the person gets fed up and leaves. If the majority doesn't want to play your way find a new strike or just help us. If im solo and the other two people want to speed run and I don't I'll leave. It's common courtesy among players. Unfortunately most people have a sense of entitlement in this game.