Overall I thought this season was well done, especially in the action scenes. But I do have some nitpicky complaints.
With the Luke Cage, Jessica Jones and Iron Fist shows, I sort of felt like the seasons were a bit too long with not quite enough action. Then the Defenders gave me what I thought I wanted; fewer episodes with a ton of fight scenes. But somehow, it was almost too much. Like RealMarchHare said, this season felt a bit short. I think the action could have had more impact if there had been some more story interspersed, and a couple more episodes of plot. Some more backstory on the five fingers of the Hand would have been nice, or some more scenes to at least make the organization seem like a more serious threat. In fact there were so many fight scenes packed into the last few episodes that I kind of started tuning them out, because they all started to look the same. Not sure if I'm just difficult to please, or if there is a happy medium in there that has yet to be found.
Jessica Jones is still the weakest link in the Netflix Universe. Her acting is fine, but she is just god awful in the fight scenes. They also didn't do a very good job of reminding people what her powers are...for anyone that didn't watch the JJ miniseries, they were probably wondering what she was doing mixing it up with the other enhanced folks. Likewise with Daredevil...they didn't do a great job of highlighting his enhanced senses, they just kind of made it seem like he has super hearing. For people that have followed the DD seasons, this isn't a problem. But they could have tossed in a couple of scenes of his "world on fire" perception of reality (or however he described it).
I kept waiting for a scene where Sigourney Weaver showcases some kind of fighting skill or special power, to justify her being the leader of the Hand. But it never came. She had no backstory, no real character development. Sig managed to give her a good screen presence, but that was simply acting skill. The character did not display anything all that evil or impressive or memorable. She was just kind of there and we had to accept that she was the leader of this supposedly ancient and all-powerful criminal organization.
I did like the Elektra turn, that was the only thing that I didn't see coming. But after that, the rest of the show was rather dull and predictable.
I hope they do another Defenders season, and I also hope that they are done with the Hand for a while. Seems like only Madam Gao, and maybe the Japanese guy are left anyway.
I enjoyed the Defenders, but I feel like it could have been better.