I think this is a good thread topic. Personally, if Talib would stay healthy, I really like Talib and Dennard at the two starting CB spots, and I think McCourty is an excellent safety. I would love to add quality depth and please, please somehow get Ed Reed here. I know he's not quite the same player he used to be, but he's still very good, and he and McCourty together would make for a dynamic, hard-hitting (yes, both guys hit), sure-tackling, and ball-hawking safety duo.
I still think the bigger need here is pass rushing. We've talked about it a million times here at patsfans, but a good pass rush makes the entire secondary better. And a bad pass rush makes even good cover guys look bad. When the QB has six seconds to throw, it's almost impossible to cover a good receiver for that long. When the QB has to chuck it almost the moment he gets to the last step on his drop back, most NFL cover guys can stay with a guy for that one second or so.
The Giants' secondary in SB 42 just wasn't very good, to be honest. They were ok. They finished #17 in the league in opponents' passer rating. They were #18 in opponent's yards per passing attempt. They were #20 in interceptions. They were #20 in passing TD allowed. They were #11 in passing yards allowed per game.
But they were #1 in sacks, and #5 in opponents' completion percentage, which is really a function of their pass rush. Individually, their secondary was filled with decent players. I mean, you wouldn't be ashamed to have them in your secondary, but they weren't standouts. But because they could really get after the quarterback, it made the secondary better than it actually was.
If we could somehow generate a much better pass rush it would improve the overall defense by leaps and bounds.