Gee Atherton won his second world title ahead of Great Britain compatriot Josh Bryceland, who finished despite breaking his ankle on the final jump.
It was MacDonald's third top-10 finish at the world championships to complete an excellent year.
Blenkinsop (Lapierre Riding Addiction, Wanganui) has been a model of consistency this year with four World Cup finishes in the top six and he produced another classy display for seventh, his fourth straight year finishing in the top-11 at the worlds.
Cameron Cole (Commencal Riding Addiction, Christchurch) impressed with 15th place in 3:29.207 while fellow Kiwis Wyn Masters, Ed Masters and Matthew Walker had solid runs.
Fourth fastest in the seeding run, George Brannigan (Trek World Racing, Hawkes Bay) was among several riders to succumb to the treacherous rocks to limp home down the field.
Manon Carpenter (GBR) edged favourite and compatriot Rachel Atherton for the women;s honours with Nelson's Veronique Sandler in 15th.
Rotorua's Connor Hamilton enjoyed an outstanding performance in the junior men;s competition, finishing fifth. His time of 3:38.736 stood as the fastest for a long time until pipped by the final few riders.
Fellow Rotorua rider Keegan Wright joined Hamilton in the top 10.
Results, Downhill:
Elite men: Gee Atherton (GBR) 3:23.769, 1; Josh Bryceland (GBR) 3:24.176, 2; Troy Brosnan (AUS) 3:24.335, 3. Also NZers: Brook MacDonald (Trek World Racing) 3:26.797, 5; Sam Blenkinsop (Lapierre Gravity Republic) 3:26.968, 7; Cameron Cole (Commencal Riding Addiction) 3:29.207, 15; Wyn Masters 3:34.763, 33; Ed Masters 3:35.276, 35; Matthew Walker 3:36.024, 39; George Brannigan (Trek World Racing) 4:04.024, 79.
Elite women: Manon Carpenter (GBR) 3:49.407, 1; Rachel Atherton (GBR) 3:49.495, 2; Tahnee Seagrave (GBR) 3:52.870, 3. Also NZers: Veronique Sandler 4:22.583, 15.
Junior men: Loris Vergier (FRA) 3:29.090, 1; Laurie Greenland (GBR) 3:34.080, 2; Jacob Dickson (IRL) 3:36.384, 3. Also NZers: Connor Hamilton (NZL) 3:38.736, 5; Keegan Wright 3:42.031, 9; Sandri Connor 3:50.265, 24; Peter Bethell 3:51.588, 26; Carl Goodwin 3:59.754, 43; Josh McCombie dnf.