Finally finished vanilla Witcher 3; Steam says 90 hours. I would say I experienced at least 70% of the content in a first playthrough. I actually stopped playing when the main storyline was 3/4ths finished as I was not finding interest in the Elder Blood prophecy thing. Aside from the main story boring me there were so many 'unexplored (?)' locations that generally gave lackluster mystery/reward that I got fed up with the lack of motivation. Don't get me wrong, there is immense effort in providing content but there were so many little stories with no start or reason to why the tomb, ancient spirit, or whatever was there...it bothered me that most of the locations were mini-stories with "missing pages".
Ultimately the combat system had great potential but it lacked a skill ceiling...either cast a sign or always wait to dodge or parry because swinging first always gets blocked even by npcs dressed as peasants (who knew all peasants in W3 were master parry swordsmen). If you don't like waiting for the computer to make the first move in melee without magic or bombs don't play W3; they'll just block and you'll have to repair your sword again and again and again.
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Not sure what game I'll be playing next. I've thought about going back to Witcher 1 to finish it and I've never played W2. I may just end up playing Savage: Resurrection and hope the Early Access ends soon