Former Brisbane Roar striker Maclaren, 23, has signed a three-year contract with the club, who have been relegated from the Bundesliga.
Arminia Bielefeld required a huge result against high-flying Eintracht Braunschweig if they were going to haul themselves out of the relegation mire.
Hannover and Stuttgart are now favourites for an instant return to the Bundesliga after second placed TSV Eintracht Braunschweig lost 6-0.
Darmstadt coach Torsten Frings said Terrence Boyd "will not play again this term."
Brisbane Roar's attacking stocks have been further decimated with young gun Brandon Borrello set to move to Europe next season.
German second-division side Hannover have sacked their general manager and sporting director to make way for former Schalke GM Horst Heldt.