The HOF committee considers many facets of how a candidate contributed to the game of basketball.
Rodman, Sampson, and Mullin were all pretty good. But I agree, Reggie Miller at least belongs on the HOF ballot if any of these 3 do.
Dennis Rodman was one of the greatest rebounders of the last 50 years in the NBA. He lead the NBA in rebounding for 7 seasons in a row (1991-1998), and is #1 in NBA history in rebound percentage. He is a 2-time Defensive POY. And he also has 5 NBA Championships (2 with the Pistons, 3 with Bulls). In
Elo rankings, he ranks as the 50th best player in NBA history. Most Top 50 eligible players are in the Hall of Fame. Reggie Miller ranks #47 on the list.
http://www.basketball-reference.com/players/r/rodmade01.html
Ralph Sampson was a dominating college player. He won the AP Player of the Year 3 straight times, the Naismith College Player of the Year 3 straight times, and the Wooden Award twice. No other player in college history has ever come close to doing that. He was Rookie of the Year in the NBA in 1984 and the MVP of the NBA All-Star game in 1985. After that, he was never a great NBA player, but injuries had a lot to do with that. He ranks at #200 on the Elo All-time list.
http://www.basketball-reference.com/players/s/sampsra01.html
Chris Mullin was a high school McDonald's All American, and an All American at St. Johns twice, and a 3-time Big East POY. He won the Wooden Award as the best college player in 1985. And he was a 4-time NBA All-Star. Mullin was a great shooter, and averged over 50% shooting for 8 of his 16 seasons in the NBA, something that is rare today for a 3-point shooter. He is ranked #66 on the All-Time Elo rankings.
http://www.basketball-reference.com/players/m/mullich01.html
Personally, I think Rodman does belong in the HOF, though because of his personal life, he might not get in. I don't think Sampson belongs in the HOF.
Mullin and (eventually) Miller are toss-ups. But I suspect an Eastern bias may work in Mullin's favor and against Miller.
The others on the ballot are:
Players Maurice Cheeks, and Jamaal Wilkes; coaches Herb Magee, Dick Motta and Morice "Tex" Winter; and contributors Al Attles -- who was affiliated with the Golden State Warriors for 50 years -- and Hank Nichols, a longtime referee, and women's player Teresa Edwards and Coach Tara VanDerveer.