Thematically, it's bang on the I'm-Too-Draconic-For-My-Shirt money.
Badass-wise.. eeh. DD is a melee class. Kicking ass and chewing bubblegum is what it does. Dragon Shaman on the other hand, is a support class. Helps friends first, kicks ass second. Barbarian/Sorcerer (or Bard)/Dragon Disciple is badass. Slap on some Half-Dragon racial paragon levels after DD 10 and you're more than golden.
However, that all having been said, there is one thing that some levels invested in Dragon Shaman could be -very- attractive for. 3 levels in DS with the proper totem? Water breathing at will. Now that's handy.