I think this board is simply a rather biased representation. People who like to moan usually do on the internet, because people can move away from them when they do it in real life. Despite the whinging about the AC Milan result ... still got further than Man U and Man City, didn't we?
The problem is that the defenders a top team has to get are not easily found. If you arent a 442 club trying to occasionally nick a draw or very occasionally win off a top 6 side, they you have to pass the ball through midfield and not just lump it forward. So, your CBs have to be able to play a bit. Get a Samba and you might be better defensively, but you will be worse going forward (although I know a lot of you feel it is hard to believe we could be worse).
Then you should have bought Cahill. Also, Samba is very underrated on the ball, he's actually very tidy with it, despite being 6 ft 4.