The win handed the Belgian world No. 11 a place in Friday’s final against veteran Croat Ivo Karlovic and extends Tomic’s winless streak, which stretches back to September.
Tomic was joined in defeat by compatriot Andrew Whittington, who only lasted eight games against Russian Mikhail Youzhny before retiring with an ankle injury.
Last-minute replacement Jerzy Janowicz, brought in on Tuesday after Richard Gasquet pulled out with an abdominal muscle injury, won his second match in 24 hours by beating Japan’s Yoshihito Nishioka 7-6 (7/3), 7-6 (7/4).
Seeds tumble at Auckland
Injury and upsets hit the ATP Auckland Classic on Wednesday, with illness forcing out top seed Roberto Bautista Agut and David Ferrer’s bid for a record fifth title ending with a whimper.
Sixth seed Feliciano Lopez also conceded a walkover, while John Isner and Marcos Baghdatis both flirted with disaster against unfancied second-round opponents.
The only seed to display any type of dominance was fourth seeded Jack Sock, who showed a clean pair of heels dispatching fellow American Ryan Harrison 7-6 (7/5), 4-6, 6-1.
Defending champion Bautista Agut of Spain was the first to exit, pulling out of the Australian Open warm-up tournament with a stomach bug before hitting a ball in anger.
His third-seeded compatriot Ferrer soon followed, shattering his dream of adding to the record of four Auckland titles he shares with Australian Rod Emerson.
Ferrer, a former world number three now ranked 21st in the world, slumped to a loss after his trademark consistency deserted him against Dutchman Robin Haase.
Sixth-seeded Spaniard Feliciano Lopez conceded a walkover after suffering back spasms during his warm-up.
Second seed Isner, the champion in 2014 and 2010, had to survive match point in a third-set tie-break before overcoming Tunisia’s Malek Jaziri 6-3, 3-6, 7-6 (8/6).
Eighth seed Marcos Baghdatis of Cyprus also struggled against German wildcard Dustin Brown, coming from behind for a 4-6, 7-6 (7/4), 6-4 victory.