I think I'm going to finish tonight. It will be about 90 hours, in comparison 60 hours for Pillars of Eternity, 55 for Skyrim, 78 for Underrail, and 55 for Divinity: Original Sin. So its a big game, but 600 hours is laughable.
Ooops for the 600H, I found the source origin, it's in game description at Steam:
"As much as 600 hours of play with hand-painted graphics and old skool goodness!"
On howlongtobeat, one report, 140H but rushed. One report you never know how safe.
In my opinion it's how a play time should always be quoted, with some comparison reference. But it's not enough, there's a problem of completionist play or not, main story only or not.
There's some balance that don't match for me in your references, PoE1 main story is no way longer than DOS main story and from very far. And your times can't be completionist plays either. So my bet is it's just your time and you have been more or less completionist, depending of the game, but this is a problem for time references.
EDIT: To temper a bit the 600H madness of the dev, I'd say that players that get help from internet got a wrong old school play time.
EDIT2: The problem of solutions on internet is the why and how find are missing, so when it's not obvious, you never know the madness that allowed the player solve the problem. It could be a hidden information in a quite different area you rushed.