@Sebinouse - It was hanging during boot (after Clover). After calming down after borking my machine, I realized my problem was with just the EFI partition, but I had no way of actually mounting it (I should invest in an msata to sata adapter). I briefly considered booting the machine with a Linux usb drive, but I've never had much luck writing to HFS filesystems with Linux and couldn't remember how the EFI partition is formatted.
Ultimately I was able to boot from a fresh Yosemite install usb drive and replaced the entire Clover directory on my EFI partition with a new one I pre-prepared. My NUC boots fine now.