Does anyone else feel like the story the DLC's bring are far, far more interesting than the main storyline? It feels like they were just going to make the DLC storyline the main one, but then realized that they could make money if they replaced that with a lesser story and sold the main storyline.

Does anyone else feel this way?

I don't think it's all just a marketing gimmick. Normally I would, but there's the fact that Ulysses was originally intended to be a companion. Are they purposefully stringing the story out through all four DLCs? Yes they are, those sly bastards. But did they intentionally put the more interesting story in the DLCs? Nah. I think the story of New Vegas is in the main game because it has more content. I mean let's face it, the actual context of the Courier's story will all take place in Lonesome Road; you could skip the other three and understand the story still. If it all can fit in one DLC, then obviously the story is smaller.

I don't think the DLC's have barely stories in them. They are single adventures that take place in inaccessible location X.
Dead Money: You get kidnapped and have to work your way out.
Honest Hearts: You travel to Zion for some reason. Violence ensues and you have to work your way out.
OWB: You are kidnapped and have to work your way out.
Main story: You are shot by unknown assailants. You must work your way to find the man who stole a mysterious chip. You must decide who to side with in an upcoming battle that will decide Mojave's fate for decades to come. You must lead your forces to victory, vanquishing all foes. Riding to sunset ensues.

That's not what I was saying.

I simply meant that if the DLCs were the main story instead of the New Vegas story, it wouldn't fit so well. The plot of that story is the plot of Ulysses, and all that Dead Money, OWB and HH have provided for that story are hints, not actual context. The actual context of the Ulysses story takes place in Primm and Lonesome Road; everything else is just filler-style sidestories.
The New Vegas story on the other hand is rather large. It effects everything in the Mojave and the quests you have to do to complete it make sense. You're running around building alliances and crushing enemies. Dead Money's story, while fine on it's own and very well-written, doesn't have anything to do with Ulysses.

And that's why the DLC storyline of Ulysses takes place over the course of the DLC: because it doesn't have enough content to be the main quest.

IMO
The main game is the story of the Mojave, and how you interact and change it.
The DLCs are your story, and how the world interacts and changes you.
I like it.