There are those touting Malik Hooker, Donovan Wilson and J Kearse as the best three-set of Cowboys safeties ever. I love their play and see how much better they are than Xaxier Woods and Jeff Heath, But, I believe it is way premature the call the KWK trio as the best in Boys' history.
I would go to the 1975-1979 trio of perennial All-Pros Charlie Waters at SS and Cliff Harris at FS, with 6'4" Randy Hughes as 3rd safety (although he started for injured Charlie Waters the entire 1979 season). At the end of the 1979 season Coach Landry said he was the best safety in the league at the end of the year.
Randy was one of the Dirty Dozen of 1975 and always seemed to have a nose for the ball and tremendous range to chase down passes. In the 1978 Super Bowl, he had 5 tackles, an interception and two fumbles recoveries.
Randy suffered a separated shoulder at the end of 1979 and it was never fixed right . From then on, he had a series of dislocations, 25 to 30 and could no longer play.
I loved Randy's play. He seemd to be always making plays and he had Charlie waters' level football smarts and instincts. He was going to be a star on his own as starter in 1980. It sounds like he had bad medical treatment and advice and/or they kept rushing him in to play when he was not not fully healed and had not strengthened the joint. Today, they can perform surgery to tighten the ligaments and muscles to prevent further dislocations.
Charlie Waters, 1979-1981 Cowboy, went to Clemson as a QB and later for his senior year started at WR, and was one of the most loved players in Cowboy history. He was like a coach on the field. He was a clutch performer. He had 41 career interceptions and holds the NFL record for most playoff interceptions with 9, including 3 in one playoff game, and has the unique achievement of blocking 4 punts total in 2 consecutive games. He also was team's holder for placekicks. In his 12 NFL seasons as a Cowboys defensive back, Waters reached the NFC Championship nine times, went to five Super Bowls and won two. He never experienced a losing season and missed the playoffs only once.