The problem is not in the backs. The backline has all the potential and firepower in the world. Although I disagreed with the selection decision at first, I think Kahui looks very strong at wing so I can't agree with your opinion there.
The problem for the All Blacks in their last 4 tests (this one included) is that the fowards are not securing any decent go-foward, they're not supporting the ball carrier and quick frankly, they look like they couldn't care less. Someone needs get every player numbered 1 to 8 and slap him hard around the back of the head. Tell them to get stuck into every ruck and maul and do the job they've been selected for.
On a side note, I don't agree about Sivivatu (although I know I'm probably alone on this) I've never liked him. I think for all the brilliance he provides, he's an equal liability when it comes to defence and ball handling. I'd much rather have Rox or Hosea Gear.