I guess another way of double checking this, is just reinstalling the Operating System from scratch at the Genius Bar.
Clearly the poster has a faulty battery.
If anything is clear it's that he uses a setting that activates the radios too often or an app that spams notifications. Without knowing anything else about his setup I'd implicate a busy push email.
And by carefully disabling every background process - what exactly do you mean? Other than mail checking - what user controllable background processes are there?
(The exception is VOIP and GPS apps, but they are not likely to be enabled without the user either being on a call or geting directions to somewhere.)
I certain I'm not the only person who has felt their iPhone get hot, and shut down everything in the switcher to recover the and stop the battery from draining?
Likewise with the iPad, making sure every music, every voip, every downloading, every geo-fence, every GPS, every-single-app is shut down is the only way I can keep my iPad Battery from draining after running a good handful of apps.
That, or just powering it down - which, as I said earlier, kind of defeats the purpose....
if you run an app and switch out then it can perform a network operation or a few other very specific tasks but they're all killed after 10 minutes anyway.
The whole multitasking part of iOS is basically smoke and mirrors. Manually quitting tasks is pretty much voodoo at this point