Yeah, the whole addition by subtraction argument requires that the replacement be better than the guy you lost. I'll buy that for Akers obviously, and Boldin is a clear upgrade over Moss, but Ginn leaving means an impact on the return game (not saying it's huge), I don't buy Walker as a total bum, and Sopoaga and his backup left. I don't care how bad we're saying Sopoaga was, until we know who the answer at NT is we can't shout "addition by subtraction!!!"
As far as the NT only playing 30% of the snaps, perhaps that percentage changes now because you...don't have a nose tackle.
The Niners are a great team, and I don't think they've been decimated here, the point that's being challenged is that Boldin doesn't erase everything else and so the Niners may have taken a very slight step back depending on whether they can fill the needs with the draft. Lord knows they have plenty of picks to do it in. But as of this very moment, they have some new holes to fill in the draft, that's all.
The Hawks didn't lose anyone of note and added 3 impact players (one high-impact player in Harvin), and the power rankings reflect this.
Now we get to see how the Niners draft. We know Schneider can build a championship caliber roster from scratch in 3 years, we'll see how the Niners do without years and years of first round picks from sucking so hard and underperforming.