The rest are more-or-less fluff - mini-DLC that placate owners of the Founder's Edition but hurt Stardock's credibility among gamers in general. They're nice in that they flesh out the game, but they're not vital for a good experience.
Eh, how so?
DLC *by definition* is 'extras' not critical to the game. They have varying degrees of "value", mostly dependent on which aspects of the game YOU personally like. You might not want to pay full-price for all them, but there's no call for saying they somehow hurt credibility. Sure, they could be combined in a new Expansion sometime, but that's $30 or so, and having them available as DLC in the mean time is entirely logical and correct.
Unless, of course, you think that companies should just hand out stuff for free all the time, forever.