YOU EARNED THEM the first time you killed Deconstructor. Exploitative game design kept you from getting what you earned until you repeated that content a random number of times until you were lucky enough to finally get rewarded for the task. It's the exact same psychological trick as 'forging. Seriously, imagine if quests only gave you an XP reward 20% of the time randomly. Or professions only succeeded to craft an item 20% of the time.

It's hilarious you would call this exploitative when the true abusive exploit is abusing people's bad ability to work out probabilities to entrap them into a cycle of doing content for no rewards. EG Titanforging on lower level content.