To clarify... area terrain gives you +2 to your cover save when you go to ground in it. It does not grant you a 2+ cover save. Most area terrain is a 5+ so you would end up with a 3+ cover save. Defense lines also give you +2 to your cover save when you go to ground behind it, but they give you a 4+ to start with, so you end up with a 2+ cover save.
Peace, Love, and Mass Destruction
Necrons in 6th Edition W: 28 L: 9 D: 5
Orks in 6th Edition W:9 L:9 D:3
F*** that, Barrel rolling monolith all the way.