This is subjective, but from the standpoint of upgrading the run defense, Eric Kendricks is an upgrade over Drue Tranquill in my view. That being said, the departure of Tranquill makes the Chargers worse from a coverage standpoint.
Kenneth Murray is also projected to probably be the second linebacker starter at a time when the Chargers are likely to turn down his fifth-year option (that didn't work out so hot for the drafted underperforming defensive starter last year). Nick Niemann, primarily a special teams feature, would see the field some in the rotation as currently constructed.
It wouldn't surprise me if the Chargers signed Troy Reeder again after the dust settles in free agency. He was great on Ryan Ficken's special teams unit this year.
But the Chargers probably need more than just Reeder depth-wise, especially with Kendricks playing through injury in Minnesota last year. He now will enter his age 32 season in Los Angeles.
It's tough to trust Kenneth Murray in the current scenario as LB2 and the depth chart behind an older Kendricks is light in general.