Dumbrell had been held high at Griffins Bend by his Eggleston Motorsport team-mate Will Brown as they battled for fourth position, which compromised his run up the hill.
It allowed Fiore to range up alongside Dumbrell and the #88 VF Commodore was turned across the nose of the #23 Nissan Altima into the outside wall.
The then-series leader somehow avoided a second hit at The Cutting as he drifted around the corner on a broken right-rear upright but did not complete another lap after retreating from the pits.
Fiore was third when the race restarted for one more lap in a time-certain finish, but drove back into the lead when Macauley Jones and Garry Jacobson dramatically ran off together at The Chase.
He therefore faced the prospect of being stripped of his second Super2 race win, in which case MW Motorsport team-mate Alex Rullo would have double his tally instead, but stewards decided that a sanction was not justified.
“The RD conducted a post-Race investigation into an incident involving Car #88 Paul Dumbrell and Car #23 Dean Fiore on the exit of Turn 2 on Lap 4. Following a review of Television Broadcast Footage and Judicial Camera Footage from Car #23 and #62 (Rullo), neither Driver was wholly or predominately to blame for the incident,” read the stewards summary.
Kostecki Brothers Racing's (KBR) miserable afternoon was compounded by 35-point penalties for both Brodie Kostecki and Jake Kostecki, both for reckless driving.
The former was punished for running into the back of Jordan Boys' Image Racing Commodore at The Chase, and the latter for clattering into the side of his brother and team-mate Kurt at Hell Corner.
Brodie Kostecki's incident played a critical role in the race, closing the field up due to the Safety Car which covered the retrieval of his stricken VF Commodore from the outfield.
Boys' left-rear tyre blew out at the end of Conrod Straight next time around as he attempted to catch the field under yellows, pitching him into the infield gravel trap.
It saw dirt left on the track when the race restarted, which may have caught Jones out when he cranked sideways into The Chase and was in turn shunted by Jacobson.
Jake Kostecki attempted an under brakes move on Matt Chahda at Hell Corner but ran long and made side-to-side contact with Kurt Kostecki, who speared through the sand trap and hit the concrete wall head-on.
None of the three KBR cars finished, but Brodie Kostecki and Jake Kostecki retain fifth and 18th in the series respectively despite the penalties.
Shae Davies was cleared of wrongdoing after a nose-to-rear hit with Zane Goddard at the same position at which Dumbrell came to grief.
Goddard caught the resulting slide, only to hit the wall at McPhillamy Park later in the lap, but stewards again found no driver wholly or predominately to blame.
The report also revealed that Thomas Randle's pit lane infringement, which saw the Tickford FGX Falcon called in for a drive-through, was due to a breach concerning crew members crossing the line at the edge of the garage.
In the unique Bathurst 250 format, crews must wait behind the line at the edge of the garage until the car arrives similar to North American motor racing, and there are restrictions on the number of people allowed across the line.
Eggleston Motorsport was fined $1000 for use of refuelling towers during the Warm Up, against regulations, adding to its horror show after Will Brown also hit the wall during the race.
Earlier in the weekend, Rullo was fined $500 for entering the pit lane after the chequered flag was displayed in Armor All Qualifying.
Three teams were also fined $500 when their authorised representatives did not attend a refuelling briefing, namely Image Racing, Matt Chahda Motorsport, and Kostecki Brothers Racing.
Despite hitting a tyre wall, Chris Pither finished third and took over the series lead in light of Dumbrell's DNF.
The series will be decided at the Coates Hire Newcastle 500 on November 23-25.
Series points Updated