To the OP's point: FONV was MASSIVELY advertised prior to its release. I DVR a lot of my regular programs and it seems that I was seeing ads for FONV for a month or two prior to its release in almost every program; more often as the release date approached. Previews galore in most of the major gamer mags and sites. If you didn't know that FONV was coming and when, you weren't paying attention.
As for DLC, I don't recall Beth doing much promo work on any of Oblivion's DLC (let's not mention "horse armor"), Morrowind's expansion packs, or FO3's DLCs. Shivering Isles and Knights of the Nine might have had ads in gamer mags, but nothing much IIRC. I think the fans got eight or ten weeks lead time from SI announcement to release. KOTN got about the same, maybe less. Same for Tribunal, but I recall Bloodmoon having several months between announcement and release. Memory could be playing tricks on me, though.
As far as I can tell/recall, Beth's traditional strategy has been to hype the hell out of the game, but go low-key (in comparison) with the DLCs. We got a rough timetable of the four DLCs for FONV and so far they're pretty much within their projected windows. So far I'm not seeing an issue. The DLC will get here when it gets here, not one second sooner or later.