Dawnguard is a shorter download. I would download that first. Play Skyrim while the giant 2 Gig extended cut downloads. I am in the middle of ME2, so I have no issue waiting.
Also aren't they adding a few stuff that weren't in the beta?
Overall screw Mass Effect. This DLC is amazing, my opinion its the best DLC i'v ever played/got. Worth it especially if your a TES fan and fan's of vampires
I'm pretty sure gstaff confirmed the beta isn't missing content that will be in the actual release.