“Marshall Dimock, emphasizing the importance of the line rather than the staff agencies, here presents a formula for the reconciliation of both... Dimock's advice, not to overemphasize staff against line, represents an emerging pattern of thought in both government and business. The chief danger in preferring staff is not merely one of neglecting the line's crucial operating experience, but the related possibility of falling into the habit of channelizing decisions and activities from all agencies through some selected staff agency, which becomes virtually the "boss's pet."”