Unless it’s Brian Blessed.  Every game should feature Brian Blessed.
True, that.  And every TV programme.
That is completely true. This is one of the reasons I didn't like Lohse voice acting as they portrayed her personality as a teenager. 
She never struck me as sounding like a teenager, just a rather "bohemian" personality, which is what she was meant to be.  That said, I still have a sort of teenage level of maturity but I was actually a teenager back around Victorian times.
Maybe not a teenager, but her dialogue was poor (notably the romance) and immature. She had such a dramatic arc that I don't think was explored well because of the way they portrayed her in the game (on top of the lighthearted tone of DOS2).  Imoen also did sound like a teenager but her dialogue and drama were better explored. 
Had the same problem for Fane. On the other hand I think they did well on the Red Prince (good match on personality/story/VO). 
For Geralt, he sounds generic to me with a Batman-ish or Solid Snake-ish vibe. W3 had solid VO, but nobody was really impressive.