2500ft/min ROD at night is begging to die. I might allow 1000, during an enroute descent, but on a final approach the max is 500, & I try for 200-300. If it gets up to 500 I start thinking about a go-around, whether it's me or the copilot flying. 2500ft/min below about 5000 AGL is just suicidal, & nobody should be surprised when it prangs in, whether it's a tilt-rotor, a helicopter, or a fixed-wing. I'm still not convinced of the accidents were caused by asymmetric VRS, it could just as easily been a rate of descent too high to stop before hitting the ground, especially the one which involved formation flight. Lead just let things get out of hand, & his wingman paid the price.