If you enable bluetooth and wifi in airplane mode, and it still stands by with no noticable drain, it might rule BT and wifi out, or identify they're causing problem.
Finding out it was a data related drain for me helped track one instance to itunes u downloads that did not show up well under the itunes U app after i had clicked. i found out those downloads were listed in another app, itunes (not itunes U), frozen while i was at home on wifi and were aparantly hitting my cell data and making phone warm like crazy as soon as I left home. Another i think it was itunes match, seemed to still be using data even though I had downloaded those playlists.
In the main settings for "Itunes & App Stores" and "Podcasts" it might help to make sure cell data use is turned off. I could have swore i had every cell data option turned off when I first had the problem, but now it helps. Also, under "General->Cellular", making sure cell data is turned off for itunes there as well (or turning cell data off for everything you don't want to use cell data for) could help. I will help tell you if it is itunes download or synch related, or passbook, reading list, etc. It is almost always a certain feature or app going haywire I found and not just "the os" in general, but an app or feature. standby with nothing going on is amazing now, so i'm very cautious leaving cell data open for these options now. If you leave cell data on but turn it off specifically for itunes & app stores, podcasts, icloud docs, itunes (the other section under general->cellular), facetime, passbook updates & reading list, it might help without interfering with carriers call & text. I just use airplane mode to see if it seems related to a data leak issue. If everything else seems fine, no accidental data leaks, I do a hard reset and it seems fine again.