When communicating with clients about progress I avoid talking about their PR/DA directly but talk in terms of improving (or not) in relationship to their competitors. They really don't care about the NY Times, but about the sites that are directly competing against them. If I can tell them that we closed the gap between their site and their competitors that is all they want to know. If a new index throws us a curve ball, we soften the blow by following up the bad news with a trend line showing that we are moving in the right direction even though there is an aberration in this indexes numbers..
Chris