I am paying to play WoW, not D3. I am not paying any more by signing up for the annual pass. I'm not paying any less. I'm also not paying for Diablo 3. I'm paying to play WoW.
I have not changed my payment plan. I have not changed the way I pay.
Just in case you missed this - I am paying to play Wow, not Diablo 3. Diablo 3 is being given to me for free.