NOW IN PRODUCTION (:
With TubeHax being relatively unreliable and going down sporadically, I spun up a highly-available Anycast constellation in the Amazon AWS Cloud that can effectively, and resiliently block Nintendo updates via the common DNS method.
My server can be used in conjunction with TubeHax (as primary or secondary DNS), adding further resilience to your WiiU's internet connection, rather than taking you down entirely if one of the servers goes down.
Please apply these settings on your WiiU device, only, not on your router.
Set Primary DNS to 52.40.86.243
Set Secondary DNS to TubeHax or 127.0.0.1