The Defenders isn't complete without Nighthawk, Hellcat and Valkyrie.
I'm not really a fan of having the Hulk, Namor, Strange and the Silver Surfer on the team at the same time.
David Kraft's Scorpio story is as good as Steve Gerber's classic run and one of the major non-Gerber highlights of the series. Actually, Kraft's run as a whole is very good and incredibly underrated.
JM Dematteis' pre-New Defenders run is also excellent.