England international Harten was in sparkling form under the hoop as the Magic bolted out to a 19-13 lead at the first break.
It was more of the same on the resumption, the Steel forced into uncharacteristic errors as a confident Magic continued to dictate across the court.
Nineteen-year-old in-circle defender Abby Erwood was on for her Steel debut midway through the second stanza in a bid to stem the Magic flow as the lead stretched out to 10.
But with the visitors enjoying more scoring opportunities and the defence line - with Jamie-Lee Price a prominent figure - limiting the Steel's attacking momentum, Magic retained their grip on the game when taking a 35-27 lead into the main break.
Lifting their intensity, the Steel stirred into fightback mode during a highly-charged third quarter to prune back the deficit.
Getting more ball into the hands of prolific shooter Jhaniele Fowler-Reid as well as big efforts from centre Shannon Francois and rookie Erwood, the Magic faced some testing moments.
Showing more impetus in all areas, Steel made inroads with extra turnover opportunities to ensure a more even contest.
But it was Harten who remained a key influence, the Magic shooter playing an impressive hand under the hoop to keep the visitors 47-42 in front at the last break.
Steel Shooting Statistics
Jhaniele Fowler-Reid 47/53 (89%)
Te Paea Selby-Rickit 10/11 (91%)
Magic Shooting Statistics
Joanne Harten 46/52 (88%)
Ellen Halpenny 13/17 (76%)
MVP: Joanne Harten (Magic)