It's even worse in iOS 8.2, as I've found that all songs with multiple composers sync as though the composer field is blank and don't appear at all on that particular screen.
I've populated all my composer fields. If a song has one composer then I sort as 'Last name, First name' and some of those have appeared on iOS 8.2 in the right place. However, on multi-composer songs, I sort those by surname only, separated by semicolons. Out of 4150 songs, 88 composer names are displayed and just three of those are multi-composer and are in the wrong place alphabetically. For instance, a Mumford & Sons song with the composer sort of "Dwayne; Lovett; Marshall; Mumford" appears under 'M', while one by The Rolling Stones sorted as "Jagger; Richards" is also under 'M'.
It worked fine before, but I have a theory that composer fields are only being displayed if they match what they say in the iTunes Store (which typically only displays the first composer if there is more than one and so is incorrect).