OK I know double posting is not allowed but I need to bump this thread.
After messing around in DDWRT I think I managed to block *.shop.nintendowifi.net and *.shop.wii.com
IDK if this block updates or not but it did block eShop (error code everytime).
You just use DNSMasq.
Save, apply and restart your router (or just dnsmasq).
EDIT: Just to be safe, do this:
Code:
address=/.shop.nintendowifi.net/127.0.0.1
address=/.shop.wii.com/127.0.0.1
address=/.shop.nintendo.net/127.0.0.1
address=/a248.e.akamai.net/127.0.0.1
EDIT2: Just tested with eShop and System Settings updater. Both returned an error.
Btw this will block for any devices under the router. So be careful if you have another Nintendo device.