There was a huge discussion about this very topic c. 100 pages ago!
Basically, this isn't an arcadey action game. It's not Souls, it's not Batman: Arkham, it's not Ass Creed.
TW3 uses ingredients from these systems (instant block/counter and instant item use of B:A/AC/SoM, quick-step dodge from Bloodborne) but instead turns it into a 'simulation' action game rather than 'arcadey'. Geralts moves take precious seconds to set up (him to build momentum), dodging and blocking is the only quick movement, 60% of whether you'll win a fight or not is if you're using the right oils/potions/bombs/signs. Positioning and gear are often more important than skill.
And Signs are basically the game-winner. Quen all day long, Yrden or Axii fast/ethereal enemies, and check the Bestiary for enemies weaknesses'.
When it starts clicking, this game's combat is the shit.
If Batman/SoM's combat is Mario Kart and Bloodborne's combat is Project Gotham Racing, The Witcher 3's is Gran Turismo.