Mass Effect story DLC is the best kind of DLC, I think. The armour sets and such are completely personal choice and not required by any stretch.
Original ME DLC was pretty bad, but I think that's to be expected considering that kind of content was really in its infancy at that point. Both Bring Down the Sky and Pinnacle Station are flawed, the former less so than the latter. But the rest - Lair of the Shadow Broker, Arrival, Leviathan, and Citadel most notable among them - are all fantastic. They aren't absolutely required for the story to make sense, but they add depth to the story if you choose to pursue it. They are also all fairly lengthy pieces and so are value for money - its a little bit of a shame that the complete trilogy + DLC was never released though (the PS3 trilogy edition is closest, but missing ME3 story DLC, Zaeed, and Pinnacle Station). Shadow Broker in particular is, I think, the best DLC I've ever played, but Leviathan is a close second. The character DLC is more mixed. Not the characters, who are fantastic. But I really think In Ashes should have been in the base ME3 game; Javik is too important to the story to be left out, plus it was a day 1 DLC too. Kasumi and Zaeed are two of my favourite characters, and Stolen Memory is great fun except for the last boss fight which is pretty silly, but they aren't as integral to the story as Javik so I'm OK with them being DLC.
Anyway, I'm a huge Mass Effect nerd (with a professionally framed poster, multiple hoodies, shirts, a mug, pop vinyls... many things) and so I'm really looking forward to Andromeda. Can't wait.