Up 22-5 with half an hour remaining, the Highlanders' defence malfunctioned as they crashed to a fourth straight loss.
The only match this week that doesn't carry any playoff implications sees the Highlanders remain in 10th place but only ahead of their conquerors on points differential, with both sides having lost seven of their 11 matches.
Three tries in the last 18 minutes of the first half looked to have done enough for the visitors but they couldn't break through the competition's worst defence in the second spell while the Lions' dominance of possession eventually told on the scoresheet.
A late injury-forced change didn't help the Highlanders, with Taranaki second five-eighth Jayden Hayward, who has barely played this year in his first Super rugby season, starting at first five in place of Matt Berquist.
It took time for combinations to click but the Lions appeared to have no answers when the teams went to the changing sheds after 40min, something that made losing even harder for captain Jimmy Cowan.
"We've only got ourselves to blame. To be up 19-5 at halftime and then come out and lose like this is gutting," he told Super Sport.
The hosts were first to score after creating a sixth-minute overlap for winger Michael Killian but the visiting forwards found their feet and the rewards followed.
Alando Soakai had their first try after exceptional work from fellow-flanker Adam Thomson, who found touch with a raking punt and tackled Earl Rose after the Lions fullback threw the ball in to himself. Thomson snaffled the ball from Rose and Soakai was rewarded for his support play.
Impressive winger Ben Smith scored after running off a Hayward inside pass and slipping two defenders while Cowan drove over on the stroke of halftime after a series of Highlanders pick-and-goes.
Fullback Israel Dagg stroked a penalty soon after halftime before his Highlanders began to be opened up by the lively hosts.
No 8 Willem Alberts crashed over for a try and set up another to halfback Jano Vermaak with a powerful burst before Rose atoned for an error-filled outing with a try that put them ahead 8min from time.
Pretorius slotted a dropped goal and his team held out a late charge from the Highlanders.
The southern franchise will seek to break their season-ending slump with victory over the Western Force in their final match at Perth next week.
