On DA DLC I can only comment from the other side of the river.
I've played all three without DLC and I never felt like I was missing anything. Sometimes the introductions are a little brief (a few characters in 2 and 3 are introduced in prior DLC) but there's tons of dialogue to get you up to speed.
If anything (especially in 1 and 2), the games were so long and involved I was waiting for it to be over. I don't see the point of throwing 5 hours on top of a 70 hour pile, not for the kind of cash they're always demanding. On the flip side though, if you've waited this long, you know the collected edition will probably be hitting $20 inside a year.
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