This is one finger of blame that everyone uses and everyone dodges. It doesn't matter how talented a rosterer you are, there will come a day when you will have to churn out something that does not fit the ideal. Fireflybob hit the nail on the head. Jobs in aviation are not all they used to be. The old days when flying was a gentleman's occupation that was done at gentlemanly hours of the day are long gone. More and more flying is taking place outside the traditional working hours of 9-5, Mon-Fri and that is a situation which is unlikely to change. Just look at how many flights are now planned to operate on Christmas Day. To add to the burden most airlines are now controlled by bean counters who work to numbers. As far as they are concerned if you can be on duty 55hours a week, 95hours a fortnight then you should be.
The modern airlines run by accountants came about because it was perceived that pilots in management didn't make for profitable companies. I personally would prefer a return to those days. At least then we may have people in charge who actually understand the impact of not having enough aircrew.