Whiteside played in Europe for a couple of seasons after leaving the Devils and before joining the Raptors. Jackson played a couple of seasons in Latin America between leaving the Kings and joining the Nets.
I'd be more inclined to pick Ennis, as mentioned above, or Doug Overton. Overton went straight from a season with the Illawarra Hawks to the Washington Bullets and stayed in the NBA for 11 seasons. Pretty much a journeyman. A bit like Rick Brunson, who played for a year in the Continental Basketball Association between his season with the 36ers and joining the Portland Trailblazers.
Chris Anstey went straight from the SE Melbourne Magic to Dallas Mavericks. His numbers were okay in NBA, for a (predominantly) bench player and he stayed for 3 seasons.
Other Australians to go straight from NBL to NBA have generally not been starters and did not stay long in the NBA. e.g., Gaze, Heal, Bradtke, Jawai.
So yes, there have been a few of successful transitions directly from NBL to NBA. Not to starting or dominating roles but to regular and meaningful bench or backup roles lasting more than a couple of seasons.