Having held Real Madrid to a 2-2 draw during the week, Philippe Clement’s men silenced the Buffalos to extend their unbeaten run to 16 in all competitions.
Senegal’s Diatta doubled Brugge’s lead after Hans Vanaken had opened the scoring for hosts in the 11th minute.
Nigeria’s Dennis made it three after 51 minutes before substitute Diagne completed the damage on the dot of 90 minutes.
South Africa’s Percy Tau was handed a starter’s role but was injured six minutes before the half-time interval and replaced by Siebe Schrijvers.
David Okereke came in for Dennis in the 69th minute with Diatta seeing action from start to finish.
Club Brugge sit comfortably on top of the log with 23 points after nine matches. They are guests of seventh-placed Royal Excel Mouscron on October 18.
