Van Duijvenbode ended a run of nine losses on the bounce to Humphries with a 6-3 victory at the MVM Dome.
The Dutchman trailed 3-2 before winning four straight legs, averaging 98 and hitting a 140 checkout.
"Luke is a phenomenal player, but I think I’m okay as well," said Van Duijvenbode after the match.
"I’m happier in life at the moment. I’ve had a lot of struggles, but I feel better. Life is better, and I’m getting better now, hopefully."
Van Duijvenbode will face Rob Cross in the last 16 after the Englishman beat compatriot Luke Woodhouse in a deciding leg.
Scotland's Anderson ended Ratajski’s bid for back-to-back European Tour titles, averaging 105.27 in a 6-2 victory.
Anderson will meet Stephen Bunting after the Liverpudlian beat Finland's Jonas Masalin 6-1.
Elsewhere, Dutch duo Gian van Veen and Michael van Gerwen also progressed following Saturday’s second-round action.
Van Veen whitewashed Hungary's Nandor Major, converting 67% of his attempts at double and producing a superb 167 checkout.
Van Gerwen recovered from 3-1 down to beat James Hurrell and set up a meeting with Nathan Aspinall, who beat Ryan Joyce 6-4 after hitting five 180s.
Ross Smith also recorded a ton-plus average in a 6-2 win over William O’Connor and will face Jonny Clayton, who beat home hero Laszlo Kadar 6-3.
Dave Chisnall boosted his hopes of World Grand Prix qualification with a comfortable 6-2 victory over Wessel Nijman.
Reigning champion Niko Springer, however, saw his title defence collapse as Ryan Searle beat him 6-4 in a contest that lasted just 14 minutes.
Searle will face Danny Noppert, last year’s runner-up, on Finals Day after the Dutchman beat Ritchie Edhouse 6-4.
Chris Dobey recovered from 4-0 down to beat Tom Sykes in a deciding leg and will face Josh Rock, who finished the day with a 6-0 win over Joe Cullen.
Jermaine Wattimena beat Andrew Gilding and will face Van Veen, while Keane Barry reached the last 16 with a victory over Madars Razma to complete the lineup.
Results
Afternoon session
Ross Smith 6-2 William O'Connor
Dave Chisnall 6-2 Wessel Nijman
Jermaine Wattimena 6-4 Andrew Gilding
Danny Noppert 6-4 Ritchie Edhouse
Ryan Searle 6-4 Niko Springer
Rob Cross 6-5 Luke Woodhouse
Gary Anderson 6-2 Krzysztof Ratajski
Chris Dobey 6-5 Tom Sykes
Evening session
Stephen Bunting 6-1 Jonas Masalin
Jonny Clayton 6-3 Laszlo Kadar
Keane Barry 6-2 Madars Razma
Dirk van Duijvenbode 6-3 Luke Humphries
Michael van Gerwen 6-4 James Hurrell
Gian van Veen 6-0 Nandor Major
Nathan Aspinall 6-4 Ryan Joyce
Josh Rock 6-0 Joe Cullen