But Willett will take a week off and then look to start the new season as he did the one just finished, by winning the Nedbank Challenge.
After starting the final round a shot behind Englishman Andy Sullivan, McIlroy carded eight birdies in the first 15 holes to surge into a two-shot lead with two holes to play, only to then find the water with an “horrendous” tee shot on the par-three 17th.
However, the four-time major winner holed from 30 feet to salvage a bogey and take a one-shot lead up the 18th, which proved just enough to secure his fourth win of an injury-hit year after Sullivan’s birdie attempt narrowly missed.
Willett dropped two shots in the final three holes, which meant he finished in a tie for fourth alongside fellow Sheffielder Matt Fitzpatrick on 13 under par.
Willett said: “I’ll stay in Dubai with the wife. We are going to just chill out for a bit and then I’ll get back to work, probably Friday, and then down to South Africa to hopefully bring back some good memories and try and defend.
“I guess if someone had said (at the start of the week) 'you’re going to finish fourth and see where that gets you', I might have taken it. As it stands, he’s (McIlroy) played some great golf all week.”
British Masters champion Fitzpatrick was one over after three holes having bogeyed both the first and the third, but three birdies and 12 pars brought him home in 70 to bank another substantial cheque – this one for €256,620 – to take his total on his first full season on Tour to €2,094,933.
Asked by what amount, if any, he had exceeded his expectations, the 21-year-old admitted: “A ridiculous amount. I was just happy to keep my card.
“You compare keeping my card to where I’ve finished on the Order of Merit (12th) it’s safe to say I just exceeded it a little bit.”
The next and obvious question was whether he had been spending any money as a result.
The 2013 US Amateur champion responded: “Not yet, no. I’m speaking to Chubby (Chandler, his agent) later, I think, about some cars. So maybe we’ll have something by the end of the day.”
McIlroy, meanwhile, hailed the best bogey of his career after surviving a dramatic lapse in concentration to win the event and claim a third Race to Dubai title in the last four years.
“It’s definitely the longest putt I’ve ever made for a bogey,” McIlroy said after a closing 66 saw him finish 21 under par at Jumeirah Golf Estates, one shot ahead of Sullivan with South African Branden Grace a distant third on 15 under.
“I don’t think there’s been one that’s ever come at a better time, so definitely the best bogey of my career. On Thursday it was a similar yardage and I was in between a five and a six iron. I tried to hit a six iron off the back foot and left it out to the right.
“I tried to do the exact same thing (Sunday), hit the exact same shot. It was 40 yards off line. It was just a horrendous golf shot.
“I guess if I had been tied playing the last, I would have backed myself with my length, but giving myself that one-shot cushion made a huge difference and I was able to just hang on.
“I’ve played really good golf this week, 13 under par at the weekend. I couldn’t think of a better way to finish the season so I’m really happy going into the Christmas break and looking forward to what’s in store for 2016.”
McIlroy missed three tournaments this summer, including the defence of his Open title at St Andrews, due to an ankle injury suffered playing football with friends and needed a controversial exemption to compete in the European Tour’s season finale after not playing enough events.
Nearest rival Willett felt that gave McIlroy an unfair advantage, but was unable to dislodge the four-time major winner from top spot in the money list. It was a position McIlroy held since finishing fourth in the Masters before winning the WGC-Cadillac Match Play three weeks later.
McIlroy walked away with a total of £2.1m thanks to the winner’s cheque and his share of the £4m bonus pool, and although the 26-year-old remains third in the world rankings, he has closed to within 0.48 points of No 1 Jordan Spieth.
Sullivan held a one-shot lead overnight and extended it to three with birdies on the first and second, but looked to have finally run out of steam on the back nine until McIlroy surprisingly threw the £5.2m event wide open once more on the 17th.
“I thought, ‘I’m back in it’,” said Sullivan. “But I gave him a great read on my (birdie) putt. I turned to my caddie and said, ‘I expect him to hole this’. That’s just the world-class performer he is.”