I suppose the question is, "Do I want this, and do I need this...?"
Need, not necessarily, want, I dunno. After the 1.4 update, vanilla Division has gotten a lot better. You can play dailies and roam the DZ or LZ and get pretty decent loot. Also, there's 2 incursions that were free with some of the updates, so there's probably more than enough content without DLC, if you're casually playing maybe 8-10 hrs/week. And with 1.5, I think there's going to be work that will better balance PvP and the DZ.
That being said, UG and Survival being completely different play experiences to the vanilla game:
• UG gives you a choose-your-own-adventure (I may be dating myself) form of game, where you pick directives (0-5) that complicate the game and number of phases (1-3) as well as a difficulty (normal to heroic) and even poof, out of the black box comes your very own "mission".
• Survival will first and foremost pit players against the elements and a clock in the form of a disease that you contract, starting you with bare bones equipment (a low level pistol and basic clothes) and forcing you to collect food, water, meds, and make your own gear. While you can play PvE, it's also possible to crank up the challenge of fighting off other players by playing in the PvP realm.
As I said, if you're not planning to play hardcore over an extended period of time, you can probably get away with the base came and the free updates it gets. However, if you're going to be playing much more than 10 hrs a week you might consider reading the DLC notes and look at reviews on UG and Survival. Also, there's a 3rd and final yr 1 DLC that will drop qtr 1 2017 that we really don't know anything about.
Hopefully the above skins some of the mud from the waters.