I think I was around 110-120 hours when I finished the game, and I didn't even do all the side content. I started out playing it pretty thoroughly but the payoff just wasn't there most of the time.
What probably added 20-30 hours for me was not paying enough attention to the crafting and skilltrees in the beginning which made the game kick my ass later on (I was playing on Hard. Which admittedly isn't that hard). So I decided to fiddle around with different line-ups, gears, armors and specs for every character. I had so much fun with that stuff that the hours kind of flew away.
And, yeah, then the game wasn't that hard all of a sudden. But it was well worth my money. Even though the combat system was pretty bad.