"It was just nice to have a chance to win a golf tournament again", McIlroy said. "In fact I actually feel like I played better once I got into contention".
Dunne finished on 20 under par to win by three strokes from Northern Irishman McIlroy, who is on course for only the second winless season of his career.
McIlroy, who was a late entry after failing to qualify for the Tour Championship on the U.S. PGA Tour, shot 67 but only after a spectator found his ball inside the five-minute time limit following a wild drive on No. 17, his eighth hole.
"Just pleased with how I'm playing and looking forward to being in the mix", he said after his round. I played well over the weekend.
That left Dunne needing to par the final two holes for victory but he birdied the 17th and chipped in for another on the last, a fitting end to a week which saw record crowds of 60,180 in attendance. That obviously gives me a sense of satisfaction to know that I can beat players of that calibre.
Only three bogeys dotted his cards over the 72 holes, the last 24 of which contained nine birdies and an eagle.
"I couldn't have done much more". I'm not going to complain. "And this year, it's something I've definitely improved on".
Hatton was out early in persistent rain and chilly conditions, but he made light of the unpleasant weather and got off to a flying start from the 10th with three birdies over his first four holes.
The Greystones man will now be a little bit richer than he was yesterday, taking home a not so shabby £500,000 with him after his heroics on Sunday.
Another birdie at the 17th following a mammoth drive got him under the card for the day, although he missed a great chance for another at the last as he settled for a 69.
"It was unbelievable to shoot 61 to win his first Tour event", he said of Dunne.
Ryder Cup vice-captain Robert Karlsson began the day with a one-shot lead and the Swede finished third on 16 under par after a final-round 66.
"He works incredibly hard at his game and I fully expect him to kick on after this and clock up more wins".
"I'm disappointed I'm not leading the tournament to be perfectly honest".