I wouldn't really listen to Kotaku, the reviewer sounded like they were trying to review Dawnguard as a separate game then a DLC.
Marketing message. While DG is bigger both in content and size than KoTN, I don't think it can rivals with Tribunal, Bloodmoon or Shivering Isles.
I hope the next 'DLC' will add a lot more.
Actually I would say Dawnguard rivals with Tribunal if not beats it, if you actually remember tribunal then you'd remember how quick it was to beat and how the writing was a bit meh and Bloodmoon's main story wasn't exactly that great either, not to mention if you beat the MQ and the EEC quests then you start to realize how dull and boring the island really is.
Have we truly http://www.youtube.com/watch?v=ZvJtSx0_VlQ?

Radiant quests = quests.
Honestly if you weren't expecting radiant quests when he said that then you're kinda stupid, no offense.