Frankly, it sounds like a scam to me. Baldur's Gate could have been "complete" too if Minsc and the quest to rescue Dynaheir were sold separately (New NPCs! New quests! New battle cries! Witty and clever dialogue! A miniature giant space hamster! Available exclusively online for only $9.99!)
As I said though, read the decription of the content and it sounds like add-on content, not real game content. It sounds like something you would release after the main game, not like something that would be a part of the game right off.
As I said in some other DLC debate, the game moves through different stages and has been done for a long time now, content wise... they spent the last 8 months doing nothing but porting the already existing content to the consoles. In that time it makes sense their artists, designers and quest makers were working on DLC, which is why it is ready at launch I would guess. Now, one could argue they should put all that into the release anyway, since it is complete, but it's not like the main game is lacking anything from the sounds of it... 200 hours? Mod tools? I think we're good.
Mod tools bring up something else... both of the main DLC "culprits" on PC, Bethesda and Bioware, release mod kits for the same games. At least they are not actively trying to destroy modding to sell their add-ons like Infinity Ward seems to be doing with Modern Warfare 2... you really don't need the DLC, you can make your own or play community made quests. It is purely optional.