You're correct with WDT daemon. I have only found one work arround for conflicting systemd-tools and udev-oxnas, is not quite elegant but it does the trick. Is just pinning those packages, i added this lines to my /etc/pacman.conf: IgnorePkg = initscripts udev-oxnas systemd-tools mkinitcpio linux-omap linux-headers-omap (Last 2 packages are optional)
Make a guide more noobish man