You spend a lot of time in combat in The Witcher 3. Trouble is, the combat isn't that good. Youtuber Joab Gilroy (best known as The Gentleman Bandit in DayZ) goes through the details of why the combat is the way it is, and follows that logic through with the conclusion that playing on Easy is the best option, core gamer or not.
I wouldn't be surprised if others had the same dilemma as me when reviewing this game. The combat needs to be critiqued. It's flawed. But the space it would take to properly critique it would take up too heavy a chunk of a review's wordcount. All things considered, it's an amazing game, and a 9.5 score doesn't gel well with three paragraphs of detailed takedown. So I'm happy articles and videos like this exist, to go into a bit more detail.
Gilroy goes into the two main schools of thought in modern combat systems, and why The Witcher 3 can't really decide which one it is. The result is a game that locks you into long swing animations against your will. Geralt comes from the school of twirling his sword around like a helicopter while running at the enemy. Mind you, this comes after the beginning scene when he criticises Ciri for being too showy.
The system doesn't give you the tools you need to solve combat problems like an enemy lunging at you. I see the enemy coming, I know what I'd like to do, but I also know if I press that button, my attack will be interrupted. You can't take control from a player, and stuff things up on their behalf. It's like driving a car and the passenger saying "I'll take the wheel for a second", and then promptly turning you into oncoming traffic.
Raising the difficulty level won't make the combat any more in-depth, it'll just increase frustration. So, seeing as this is one of the extremely rare games in which story carries its other elements, no matter how core a gamer you fancy yourself, Easy might be the best path.