And it's also EXACTLY because it's TV show we can expect the survivors to recover no matter how screwed up their work are, damn it. In 7 seasons of line of duty, Jack Bauer gets his wife shot, his daughter kidnapped, his girlfriend mentally retarded, and his bestfriend disavowing him. Why in Day 8 he still returns to CTU? Why won't he say 'F this crap! I'm leavin!'? Because he's Jack Bauer! Because he's badass! Because it's a TV Show! People can recover from sadness and grieving all the time.
Sam, G, Kensi, Deeks, Eric, etc, are not Jack Bauer. They are not supposed to be him. 24 was interesting the first few seasons, but after that, it started getting VERY depressing; BECAUSE Jack kept losing people around him. Sam, Kensi, and Eric are interesting, because we DON'T know everything about them. The writers are gradually showing us more about the characters. The team is a good one. Their different character traits complement each other very well. Killing off 50% of the team wouldn't just cause extreme stress to G, Hetty, and Nell. It would depress the audience to the point that the show would be cancelled. This is not 'Day of the Condor', or 'The Manchurian Candidate'. This show is intended to be a more lighthearted escapist espionage fare.