Rule of thumb is to take your descent angle (3 degrees typically) x mach number = VVI descent.
.80 x 3 = 2400' per minute descent.
At 250 KIAS at low altitude 757/767's tend to descend around 1300-1500' FPM.
3500 FPM isn't dangerous unless it's really low. High speed arrivals and a desire to descend quickly sometimes causes descent rates like that below 10,000 AGL.