Following on from Warrington's heavy loss to London on Friday night, it looked as though both Wembley-bound sides would be heading to the capital on the back of heavy defeats when Leeds trailed 18-0 and 32-12. But a stunning turnaround ensured the game was only won in the dying seconds, despite the home side having held a 20-point lead with 20 minutes remaining.
Setaimata Sa, Scott Dureau, Remi Casty (two), Vincent Duport and Daryl Millard were the try-scorers for the Dragons, while Shaun Lunt, Ben Jones-Bishop (two), Ryan Hall, Jimmy Keinhorst and Jamie Jones-Buchanan touched down for the visitors.
In the day's other match Widnes turned on the style in the second half as they hammered Hull FC 42-20.
Hull were still in it as they trailed 20-10 at the break but thereafter the home side cut loose, with Willie Isa and Shaun Briscoe managing two tries apiece and Paddy Flynn, Frankie Winterstein, Danny Craven and Rhys Hanbury also touching down.