I would not contest that this may be a fatiguing work pattern, but at the risk of being flamed would suggest that you can't really ask to fly three nights in a row and then complain about being fatigued. Whilst it may not be fashionable to defend Flydubai in this thread, I am far junior to both of these guys, but on the same day operated a much easier flight ending about 9pm local time, so presumably had they bid for day flights they would have got them, as I did.
The pilot can't complain about being fatigued because he is deceased.
Many of the comments in this thread, if truly representative of industry operations and perceptions, indicate the aviation industry is lagging a long way behind other high risk industries when it comes to understanding and managing fatigue.
Humans are notoriously bad at responding to fatigue, it's why driving and resting times in the heavy vehicle industry in most advanced economies is heavily regulated.