I understand your frustration as I too was unable to do a multitude of things via wifi (connect to the eShop, Netflix, download a simple game update, etc) without my signal dropping... Many people have suggested that I hard-wire my Wii U to my router, but guess what? The whole point of creating a wireless network is to take advantage of having your wireless router in a central location (ideally) in the house (making it fairly accessible to other devices) and your wireless device separate and remotely from your access point.
So after much frustration and headaches I came up with a reasonable solution that won't cost an arm and a leg and won't require you to relocate either the Wii U or your wireless router.This cost about $50 all together and it only took about an hour (trip to the store for parts and setup). So if you are willing to have a bit of patience I believe that this will work for you too.
The first item that I bought (found at my local Wal-Mart) was the "TP-LINK 150Mbps Wireless N Mini Pocket Router Model No. TL-WR700N. This was $29.99 + Tax. The reason this item was important was because I realized that this little guy could work as a router, a repeater, a bridge, an access point, and my favorite and most important part of all a Client Adapter. Essentially the description it gives is as follows, "Give wired-only devices access to an existing Wi-FI network."
I understand that the Wii U is not a wired-ony device, but in order to make this solution work you will need to turn the Wii U into just that. So we will find out exactly how to do that in the next step. The reason for this is because the Wi-Fi chip that is built into the Wii U is not all that great as countless forums have proven this to be the case. Hopefully they will consider this when the Wii U gets a makeover later on in the console's life as so many other Nintendo systems have done before in the past.
The second item we need can be found at your local Best Buy.This is the "Rocketfish Gaming Nintendo Wii LAN adaptor." So a couple of things to point out with this nifty little gadget is that it is in fact compatible with both the Wii and its successor the Wii U. Also I believe that you can only find this at Best Buy or bestbuy.com as they are the parent company of all Rocket Fish accessories. This ran a total of $19.99 + tax. We will now tie this back into the earlier point of turning your Wii U into a wired-only device.
The reason this is so important is because this item will take the place of your Wii U's internet port essentially bypassing the internal Wii U wireless chip and instead replacing it with a two-fold solution. In other words, you will be plugging in your "Rocketfish Gaming Nintendo Wii LAN adaptor" into one of the USB ports located on the back of your Nintendo Wii U. Next you will plug the LAN adaptor into your "TP-LINK 150Mbps Wireless N Mini Pocket Router" using a supplied CAT-5 ethernet cable. And just like that you now have an external Wi-Fi connection that does not require you to move any devices and eliminates the need to use the Wii U's internal Wi-Fi chip.
Rocketfish Gaming Nintendo LAN adaptor
TP-LINK 150Mbps Wireless N Mini Pocket Router
LAN adaptor plugged into TP-LINK Mini Router (setup as Client Adaptor Mode) via CAT-5 cable.
And just like that you now have an external Wi-Fi connection that does not require you to move any devices and eliminates the need to use the Wii U's internal Wi-Fi chip.
****As a side note you will need to program the TP-LINK 150Mbps Wireless N Mini Pocket Router before you begin installation. The easiest way to do this is by pluggin the device into an outlet and logging on to the router's default broadcast SSID. Simply grab the nearest laptop or Wi-FI enabled PC or Mac and bring up the Wi-Fi Utility. Essentially what you need to do is find the default broadcast SSID which in this case was "TP-LINK_C6906F." The password might be different for each unit, but it does come printed on a handy little card.
Next you will need to follow the instructions very carefully. Once you have logged onto the default broadcast SSID, which in this case was "TP-LINK_C6906F, you will need to pull up your internet browser and type in the following address: http://tplinklogin.net. Before access is granted you will need to be authenticated. The username and passwords in this case will be admin and admin respectively.
Now once you are inside the "Web Management Page" you will be prompted to Select a Mode. In this particular case we want to select ***Client***.
Once you have selected the Client mode you will then hit next and it will ask you if you want to reboot in which you will reply yes and proceed to the last step.
Once you have the LAN adaptor plugged into TP-LINK Mini Router (setup as Client Adaptor Mode) via CAT-5 cable you will need to do the final step. Turn on the Wii U and go to System Settings > Internet > Connect to the Internet > (Press "Y" in the upper left hand corner to bring up the Connection Types > Lastly Click Wired Connection. It should then test the connection and as long as you followed my instructions earlier it should display the following message...
The Connection Test was Successful... Congratulations!!! You can now stream information wirelessly to your Wii U without a fear of dropping signals or having to rearrange your entire Wi-Fi setup in your home or apartment.