It was a win Ulster hardly deserved after a Dragons side, who were reduced to 13 men at one stage, took the plaudits with some superb defence and lively play behind the scrum.
Dragons led 10-7 at the break and looked to have secured victory until Jackson’s big boot spliced the uprights with 90 seconds remaining.
Dragons fired from the first whistle — the visitors had sweetly moved upfield and fly-half Angus O’Brien popped over a simple penalty.
Ulster found the Dragons’ extremely quick first-up defence hard to penetrate. Then when Dragons’ right wing Ashton Hewitt broke through a succession of weak tackles deep in his own half in the 16th minute, Ulster’s defence was stretched and centre Adam Hughes was on hand to slide in at the corner on a grubber kick by Adam Warren with O’Brien adding the extras.
Ulster, though, came storming back again, this time they had the patience to find a gap out wide on the left for flanker Sean Reidy to burst through a Hewitt tackle and race in at the corner. Humphreys converted from the touchline.
With returning Irish duo Stuart McCloskey and Paddy Jackson entering the fray at the break, Ulster did start with a flourish, but is was Dragons who again took advantage of some inept tackling to go further ahead with Carl Meyer touching down to give the visitors a 15-7 lead.
Ulster again were back in the hunt with a penalty try after Dragons lock Matthew Screech pulled down a forward drive destined for try. He got a yellow card for his troubles as did Ben White soon after for a dangerous tackle on Peter Browne.
Outnumbered, but the Dragons defence was very stubborn and Ulster just could not break them down. It looked as if was not Ulster’s night with two disallowed tries, and Jackson’s 70th minute penalty bouncing the wrong side of the crossbar. But then the fly-half had the nerve to do the needful with his final effort at the end.
Tries: Reidy, Penalty. Cons: Humphreys, Jackson. Pens: Jackson.
Ludik, Gilroy, Cave, Olding, Stockdale, Humphreys, Pienaar, Black, Herring, Lutton, O’Connor, Browne, Diack, Reidy, Wilson.
P. Marshall for Olding (66), Jackson for Humphreys (41), McCall for Black (49), Andrew for Browne (56), Williams for Diack (41), B. Ross for Reidy (53).
Tries: Hughes, Meyer. Cons: O’Brien. Pens: O’Brien.
Meyer, Hewitt, Hughes, Warren, Amos, O’Brien, C. Davies, Price, Dee, Harris, Screech, Landman, White, Cudd, Jackson.
Stankovich for Price (57), Knight for Harris (64), Hill for White (67).
Bath 11 Gloucester 15