I generally like the DLC characters, though, partially because Sydney is cute.
Personally I'd have it as the Original 4 + Houston as the main characters, with one of the DLC characters per episode. Then for the rest of the supporting cast there's Bain, Twitch, Gage, Bile, etc. Captain Winters and Hector
can be reoccurring villains, as well as Locke as a more shifty, ambiguous type.