I've thought this for awhile myself; there's just no one on the backend that the opposition has to worry about launching missiles from the point. They're too slow at getting effective shots off, and when they do they are, as you say, weak or blocked, or they're a mile wide. The forwards routinely seem to get outnumbered on the boards in offensive zone because the other teams' forwards know they can cheat down to help, because even if the puck does come out to one of our dmen, they'll fumble it, or take fifteen minutes to settle the puck and get their shot off.
I've been unwilling to hop on the Big Buff bandwagon because big bodies with lots of miles on them seem to go off the cliff in a hurry--even physique freaks like Chara, and Buff ain't no Chara; and Holland's recent track record concerning trades has been trending ever further into disappointment-land--but man, does this team need desperately that kind of offensive presence back there.
At this point I think I'm willing to take the risk because watching a team with Nyquist, Tatar, Larkin, Datsyuk, Zetterberg, Richards and Green on it struggle to score even two goals every night is pathetic, and downright boring. Sure the latter four aren't what they used to be, but we've seen all of them are still smart, creative players and if they had just the little more space and time that an extra presence like Buff could afford them, we'd probably see a lot of our current ills resolved. Pulks and Sheahan might start producing, some of our other dmen might even start producing. We know at this point shuffling forwards around like deck chairs on the Titanic isn't going to fix it. And Kronwall returning won't either--so no, Holland, Kronwall isn't our trade-deadline acquisition. Time for a meaningful shakeup.