Well, on one hand I agree that the voices of Triss and Dandelion in TW2 weren't all that great, on the other hand I thought they did a great job in imitating their counterparts from TW1. I wonder if they were intentionally trying to sound like the "original voices," so to speak. Sadly the originals are basically flat, nasal generic American accents.
Regardless, if Triss or Dandelion suddenly sound Welsh or something in TW3 it will be much more jarring, no matter how talented the actor. Too late to give their voices a radical overhaul, ya know?
I also hope they crank up the bass and the volume in Doug Cockle's recordings for Geralt in TW3. He practically boomed through my stereo speakers in TW1, while in TW2 his voice sounded weak and thin, and was often so much softer than other voice actors that I would have missed what he said if I didn't have subtitles.