Hoffa's season-best throw of 70 feet, 41/4 inches bested Tomasz Majewski, of Poland, who tossed 69-63/4.
Christian Cantwell, of the United States, finished third, losing his first shot put event of the season and ending a 20-meet unbeaten run dating back to September.
Cantwell had been looking to join women's high jumper Blanka Vlasic with six consecutive victories in the Diamond Race.
Allyson Felix and Jeremy Wariner, of the United States won 400-meter races.
Felix held off new European champion Tatyana Firova to win in 50.79 seconds. American Debbie Dunn was third.
The 24-year-old Felix earned her second victory of the meet after a win in the 200 on Friday.
"The time wasn't great, but it wasn't about the time today," Felix said. "It was a great field, and I just wanted to execute my race. It was more difficult than yesterday's race."
Wariner beat world leader Jermaine Gonzales, of Jamaica. Wariner lagged for the first 200 but powered past Gonzales on the final curve and held off a late challenge from his rival to finish in 44.67.
Wallace Spearmon of the U.S. clinched his first Diamond League victory of the season, clocking 20.12 to win a low-quality 200.
"I ran a little slower than expected, but it was still a good race considering the wind," Spearmon said.
David Oliver won the 110-meter hurdles in 13.06. Women's 100 world leader Carmelita Jeter was upset by Mershevet Myers, who won in 11.01.
Double-amputee sprinter Oscar Pistorius set a new world disability record of 47.04 in the 400, racing against other amputees.
"I really had to rely on my endurance," Felix said. "I felt pretty good, but it was a little difficult recovering (from her specialty event 200)."
Firova finished in 50.84. The Russian was trailed by Dunn another 0.05 back.
Mariya Savinova, of Russia, eased to victory in the 800 in 1:58.64.
Kaliese Spencer, of Jamaica, climbed into third place in the Diamond Race for the 400 hurdles, crossing the line in 53.78 to claim a third consecutive victory .
Milcah Chemos, of Kenya, posted a meet record in winning the women's 3,000 steeplechase in 9:22.49.