Same behavior here on Asus X99 Deluxe since 10.11.4 with Samsung 950 PRO 512Gb. I also tried with 10.11.5 and on several motherboards (Z9PED8 WS and X99-E-WS) with and without Asus PCIe board adapter.
The OS boots up but if I try to browse the M2 content I get an instant reboot (kernel panic related witch backtrace to NVMeGeneric.kext).
It's a shame JimJ740 does not answer or release the sources from his driver. It's conter-productive : he made a poison gift that lead to this point where no one want to put together a proper open-source driver for mac as the work has already been done.
Anyway if anyone needs some testers you can just PM me and I will be glad to help the best I can.