In truth I hated DA:A because it was always so buggy and it annoyed me how often I had to exit the game and go back in when things got super laggy (it would have been finished so much quicker if I didn't have to do that so often). If I wasn't such a lore junky and wanted the full story and quests in DA2 I would avoid it all together. Granted I would avoid all the DLC for Origins (Which I actually only do Awakenings and Witch Hunt -- and I have yet to see Witch Hunt actually effect any DA2 changes)
I think you MIGHT miss out on a little banter with Anders in Legacy (I think) where he mentions Sigrun, a character from Awakening.
All depending on whether or not you did Awakenings, you have two different banters (this may also be effected on whether or not you recruited her too).
If you did: You get the banter where Anders will actually remember her name and comment about her personality.
If you did not: You get the banter where Anders will mention meeting a girl from the Legion of the Dead once. But he can't remember her name
Also in the Legacy DLC all depending on choices made with The Architect changes dialogue when confronting the Wardens (I can't remember the lead Warden lady's name) and they talk about Corypheus. Anders's dialogue will change depending on the choice The Hero made.
I'm not sure if you lose out on other party banter, like for instance banter between Merril and Anders if you imported a Dalish save. I know there are two different banters depending if the Dalish Warden lived or was killed defeating the archdemon. Like I said though, I don't know if doing DA:A effects this or not.
So, you're not really losing out on anything in DA2 skipping over DA:A. Now in DA:I, that another question entirely. But with Keep, it won't really matter anyway.