are you kidding me? the y cable is not only recommended everywhere! it is mandatory! get it or get out!
I used the very same hdd on my old wii with a normal cable and it worked lol. Ive ordered a Y cable off ebay but not without trying to find one locally. Ive got another 2.5 external hdd that Im going to use on my daughters wiiu once Ive got this pone up and running. I'll just install a back up to the sd card ive got and try it out.