No new places to visit, but there are new enemy variants and some interesting/challenging missions. Silver Spiders are great for farming since they pretty much guaruntee 3 drops for every one you kill. They are just regular spiders that are silver/metal colored with around 10x the health and deal more damage.
For instance, here is a video i made a while back for farming the silver spiders on mission DLC 2-16:
http://youtu.be/gqZIMDsmalg --- Future, Fate, Predestination, Fortune, Doom, Luck, Karma, Serendipity, Finality, God's Will, What is written, World to come... DESTINY PSN ID: NiNeBReaKeR87
Mission Pack 2 DLC is worth the money only for stage #16 which will speed up your armour & weapon farming. The stages themselves are "super-hard-mode" stages and by that I mean very, very unfair. I'm not even going to try and beat them on Inferno, it would be impossible in one-player mode. But to save you time... it is worth the money.
I found at the weekend there is a GREAT armour farming method on DLC 3 stage #2. At this point in time you won't have the Master Rapier to perform it (basically pointing up at the sky on top of an ant hill that spawns silver spiders, and wrap and elastic band around the trigger). But you could just run around killing the spiders once all the other nests are destroyed and leave just one. Would strengthen you in no time.
Actually, Fencers with a pair of Jackhammers can do DLC 3-2 farming even easier than WD. Just start the 2nd Jackhammer halfway through the 1st, so there's always one firing. I only played the 1st DLC through once. From what I remember it had some interesting variations & tactics, but nothing special (it's also pretty short). DLC 3 is insanity. If you ever wanted to feel just completely overwhelmed, DLC 3 is for you. --- Protecting the green Earth, if even for a single flower.