IMHO, the "1/11" case is simply an incorrect tag and you shouldn't have to code around it.

I say, give them the "playlist position" field as well as the track number field, like Jemplode does, and all will be well. I have no trouble getting proper track titles when using the Position field, as long as I've got one playlist per albums. In my case, position is a more reliable number than the track number field.