Gravesend were reduced to 10 men in the second half when Sturgess was dismissed for a professional foul.
Munster flanker Frankie Sheahan was sin-binned for a professional foul in added time and Sexton converted the resulting penalty.
BBC: Ronan O'Gara is tackled by Stanley Wright and Trevor Hogan
Mendez was yellow-carded in injury time for a professional foul - a deliberate knock-on that killed a promising Exiles move.
The Clarets were in trouble as early as the sixth minute when Clarke Carlisle was sent off for a professional foul.
Mafi was then yellow-carded for a professional foul at a ruck, handing Parks the chance to reclaim the lead for the Warriors.
Kevin Thomson was sent off for a dangerous tackle on his namesake Steven and Danny Wilson saw red for a professional foul on Craig Dargo.
It was initially thought that Halsey had dismissed Terry for a professional foul on Jo, but he later clarified that the offence was "serious foul play".
Leverkusen survived a late fightback to win 3-2 away to defending champions Wolfsburg, who had goalkeeper Diego Benaglio sent off for a professional foul on Eren Derdiyok after only 31 minutes.
Leeds had England forward Jamie Jones-Buchanan placed on report for a crunching tackle on Saints front rower James Graham, while St Helens' Leon Pryce was sin-binned for a blatant professional foul.
The hosts were never in it after Craig Morgan saw red for a lunge at Campbell, and Ryan Bennett was then sent off for a professional foul on the same player.
But Halsey's decision to issue a red card for serious foul play rather than a professional foul meant the position on the pitch and the presence of other players were not relevant.
Everton drew 1-1 at Czech side Sigma Olomouc for a 5-1 aggregate victory despite playing all but the first seven minutes of the match with only 10 men after full-back Tony Hibbert was sent off for a professional foul.
Two Butch James penalties stretched Bath's lead, and Leicester, who failed to get into Bath's 22 during a woeful first-half effort, had their job made all the harder when Ayoola Erinle was sin-binned for a professional foul at the breakdown.
The defeat dropped West Ham back into the relegation zone and Hammers boss Avram Grant believed Vidic should have been sent off for a perceived professional foul on Demba Ba rather than the yellow card he received when the visitors were trailing 2-0.
应用推荐