I'm an avowed DA2 apologizer, so I'll just get that out of the way right now.
Legacy: Barring Lair of the Shadow Broker, probably some of the best DLC BioWare has come up with in terms of overall challenge, story, and writing.
Black Emporium: Now, I know a lot of people are going to raise a brow at this, but this put in some well needed options, especially in DAI, allowing me to change facial features and SELL TIER 4 MATERIALS. That alone was a godsend since the material dupe glitch was fixed(it was nice when the game didn't make you grind for everything)
Awakenings: I actually liked the story, and I have fondness for Sigrun and Nathaniel. Also, Awakenings Anders is the best Anders.
Descent: Good, leaves a lot unquestioned that I'm going to assumed will either be brought up in the next DLC or next game, but it was kind of a bait and switch when it was advertised as relating to the Darkspawn. I didn't. At all, which was a letdown.
Jaws of Hakkon: I wish there had been more of story, beyond at the very end, but what was there was good. Also, would've been nice if we were given more Ice Dragon Bone and Veil Quartz than for more than just one or two items. Put that **** in the Black Emporium, AT LEAST.
Golems: I actually liked the strange, color-related quests and overall creepy feel. Sorrynotsorry.
Shale: You buy it for the companion, not the quests that go with it. Shale is the best.
Ostagar: I got it for Duncan's weapons, but bringing closure to Alastair and Wynne was good.
Warden's Keep: Would be higher for the simple fact of getting the party storage chest. And Space Sword. This really SHOULD be higher, but everything else is better. I also liked the blood-related abilities.
Mark of Assassin: Sorry, I can't stand Felicia Day in any form. And her character looks kinda strange in the face. Only thing good about it was the challenging boss fight at the end.
Witch Hunt: **** that DLC. It is not worth your money for the whole two hours of gameplay and ten fsking minutes with Morrigan. Which in the end, tells you absolutely NOTHING. I actually LOST respect for BioWare after playing that because it came off as little more than a cash-grab.
Darkspawn Chronicles: Never played, also seemed like a cash grab, even if in a 'what if' scenerio.