Thanks. Your kext solved my usb problem in yosemite. i dont know why but in el capitan works perfectly without any edit or kext.
From what I see, 10.11 has a more flexible USB system. The ability to override ACPI via plist is helpful. Seems as if pre-10.11 had hardcoded configuration depending on Mac model, new code is more flexible/data driven/ACPI driven.
On 10.11, without XHCIMux, are your USB devices attaching to XHC or EHC1?