I think the Eagles present the biggest problems for the reason that they still have a very explosive offense, that can score points in bunches (Having Westbrook and Jackson and now adding in Maclin who doesn't have to come right in and be a hero), so while their defense will struggle without Dawk and Johnson, their offense could win some shoot outs for them. I think the loss of Dawk will be a huge loss for them, heart and soul wise, and they'll probably stumble out of the gates because of it but will have that part figured out by mid year probably. Just in time to give us fits late in the year.
The Giants lost their DC, which will hurt, but more importantly they lost their top 2 WR's and they're basically going to be banking on a bunch of guys who couldn't get it done last year without Plax, and now they don't have Toomer either, or a couple rookies coming in and lighting the world on fire. Their offense is going to struggle MIGHTLY. Especially late in the year, when you really need to be able to grind the ball out with running.
Theyr'e going to see pretty much everyone put 8 in the box and dare them to have Eli try and beat them with a bunch of young, unproven, WR's. It's going to be very, very, very tough.
Defensively they'll probably start slower but by years end their defense will be the only thing keeping them in games.