So after flashing the "main" (unbranded version) ROM, WiFi was actually broken. I took the wifi files from /system/etc/wifi from the Sprint-variant (this thread), and pasted them into the GSM rom. Fixed permissions @0644, reboot... WiFi fixed.
In case anyone else out there is on a Sprint GSM-Unlocked N3, you can run Lollipop with your MI3/MJ4 modem. Just flash the GSM-based port (mentioned in OP), and replace the /system/etc/wifi within this
zip (it is NOT flashable).
---------- Post added at 03:27 PM ---------- Previous post was at 03:25 PM ----------
Like I said in the quote, I did a full wipe. Are you trying to get GSM working on the Sprint variant? Please note that I flashed the ROM in the other thread, not the Sprint ROM. Now I have full GSM Data, MMS, and WiFi working. I supposed I should test GPS, but meh.

I no longer have Sprint service, nor do I use CDMA, so I won't be much help if you need Sprint data working. But if so, then everyone says to flash the build.prop posted in OP.