With the exception of the bloody baron quest, every quest in the witcher is: theres X monster in Y place. You go to Y and discover that the X monster is not there anymore. Use your witcher senses to find where X monster is. You find X monster, kill it and then come back for reward.
Yeah i know exactly how your feeling, i NEVER complete games like that, im not a trophy hunter but with Witcher 3 i did exactly the same...and when it was over...so sad, nearly no game can touch Witcher 3´s singel player greatness