Gaetano Berardi was shown a red card at the end of a desperate first half which saw Cardiff score three times and Pontus Jansson leave the field on a stretcher.
United were already 2-0 down when Berardi was booked for a second time after fouling Gary Madine in injury-time.
Pierre-Michel Lasogga had earlier hit a post and the crossbar after Paterson’s ninth-minute header gave Cardiff the lead but Neil Warnock’s side exploited woeful defending to kill the game before the interval.
United’s problems increased midway through the first half when Jansson was carried off after a off-the-ball clash with Sol Bamba, adding yet another centre-back to the absentee list, and Hoilett’s sliding finish on 41 minutes left Leeds facing up to a sixth league game without a win.
Berardi was then sent off and from the resulting corner, Morrison guided home another free header.
Christiansen’s players were briefly given hope on 55 minutes when Bamba turned a Stuart Dallas cross into his own net but there was no way back from an overwhelming deficit and Anthony Pilkington wrapped up Cardiff’s win two minutes from time.
Christiansen said Berardi should have shown more intelligence after he was sent off.
It was the Swiss defender’s fifth sending off in his Leeds career.
Christiansen said: “I’m disappointed with it (the sending off) of course I am. Firstly because he already has one yellow card when he goes down to the ground. He should have been more intelligent, but it’s the passion and emotion he plays with.”
Matthew Pennington had spared Christiansen from an immediate defensive crisis by returning from injury and partnering Jansson at centre-back but Leeds looked shaky from the start and were behind after nine minutes.
Christiansen had warned that Cardiff’s superior height might be a factor and United’s struggle to cope with deliveries into their box was underlined by Paterson’s goal.
A corner from Joe Ralls caused chaos in the home box and Armand Traore took advantage with a whipped cross from the left, allowing Paterson to head home from close range.
Leeds could have been level soon after when a 25-yard shot from Lasogga was brilliantly tipped onto a post by Cardiff goalkeeper Neil Etheridge but Cardiff wasted a glorious chance with their next attack as an unmarked Yanic Wildschut nodded over an exposed goal from six yards out.
United were thwarted by the woodwork for a second time on 26 minutes when Lasogga, teed up by a perfect cross from Pablo Hernandez, headed against the underside of the bar. The rebound fell kindly to Gjanni Alioski but his volley into the ground was clawed away by another superb reaction from Etheridge.
Jansson was then stretchered from the field on the half hour following a coming-together with ex-Leeds captain Bamba inside Cardiff’s box and Etheridge held a low shot from Jansson’s replacement, Stuart Dallas, to keep City in front on 38 minutes.
The visitors then extended their lead as poor defending from Pennington allowed Paterson to shoot towards the far post where Hoilett slid into finish from a tight angle and after Berardi was shown a red card, Morrison rose to head home the free-kick that followed.
Leeds had fought back from 2-0 down against Millwall in their previous home game to lead 3-2 with 10 men and Bamba perked up a frustrated crowd 10 minutes into the second half when his attempt to clear Dallas’ low delivery sailed into the top corner of Etheridge’s net.
United were unable to force the issue further, though, and amid mounting frustration, Christiansen faced chants of ‘you don’t know what you’re doing’ from section of United’s support after replacing Lasogga with Hadi Sacko 16 minutes from the end.
Leeds United: Wiedwald, Berardi, Pennington, Jansson (Dallas 30), De Bock, Forshaw, Vieira (Grot 86), Alioski, Hernandez, Roofe, Lasogga (Sacko 74). Subs: Lonergan, Anita, Pearce, Vieira.
Cardiff City: Etheridge, Ecuele Manga, Bamba, Traore, Grujic (Halford 82), Paterson, Ralls, Hoilett, Wildschut (Pilkington 55), Madine (Zohore 72). Subs: Murphy, Feeney, Damour, Ward.
Referee: Graham Scott (Oxfordshire).