I think that's the point with Olgierd though. He's supposed to come off as just another bandit at the beginning. Once you get to know him, he becomes a much deeper character.
Definitely agree with you on O'Dimm. I don't really want to elaborate since it's hard not to go into spoiler territory, but suffice to say, he's one of the best characters I've seen in a video game in quite some time.
One thing that should be mentioned IMO is that the sound track here is probably even better than the base game's and helps sell a much creepier atmosphere. At times, I felt like I was playing a Lovecraftian horror.
Edit: Also, just to compare this quest line to those from the main game, I'd say this is the best one so far. Even beats out the Bloody Baron story IMO.