That just 10 per cent of the field of 40 made it to the finale was testament to the difficulty of the course in Belgium, with a number of top riders falling short.
Christian Ahlmann and Gerco Schröder picked up nine penalty points, and Jos Lansink, winner of the Grand Prix the previous day, had five to prevent their progress.
Even Edwina Tops Alexander, riding Ego van Orti, found the path to the jump-off too treacherous and, with one penalty point, she had to settle for fifth.
Meanwhile Hans Dieter Dreher and Reed Kessler withdrew.
Joining Deusser, who was riding the 10-year-old Westphalian gelding Comet d'Amour, in the jump-off were Dutchman Jeroen Dubbeldam on Zenith, Sweden's Jens Fredicson on Lunatic and Spanish rider Lucrecia Cordon Pilar with Nuage Bleu.
Pilar went first and cleared in a time of 37:94 seconds before she was bettered by Fredricson's clear round in 36:43s. Deusser then laid down the benchmark time of 35:66s and when Dubbeldam withdrew on the next run, victory was the German's.