Finished watching Luke Cage today and pretty much agree with everything written here. Diamondback was definitely a weaker character than cottonmouth. The final "battle" between Luke and Stryker was pretty stupid...surely Luke would have realized that all the power for Strykers suit came from the thing on the back, so why didn't he just destroy that at the start?
Black Mariah was probably the best villain of the series, and Alfre Woodard was awesome in the role. Simone Missick was great as Misty Knight too. But overall the series didn't drag me in as much as Jessica Jones and both Daredevils did.
Considering the number of antagonists still alive so far (Kingpin, Stryker, Black Mariah, Shades, Elektra, The Hand, Madam Gao), it'll be interesting to see who gets involved in the Defenders cross over, and how they relate to Sigourney Weavers unknown character