I have never met a HTML5 test that is remotely accurate personally, on Wii U, PC, or otherwise.
Its also known that the Wii U WiFi is capped at 65Mbit, although that should mean its "theoretically" capable of about half that depending on if your neighbors are using the same channel. (being a radio signal, everyone on the same channel share the same pool of bandwidth even though they are different networks)
As I said in my WiFi thread, I would recommend using the LAN adapter and a good USB stick or external HDD for optimal download speeds. But even with the LAN adapter I would be pleasantly surprised if you reached 35Mbit as in my experience the Wii U just doesn't go that fast.
Edited by Alex Atkin UK, 13 September 2013 - 02:19 PM.