The voice acting is a bit of a mixed bag. I don't like Minfilia's voice either, nor do I like Yda or Papalymo. But Thancred's voice acting is good, and Merlwyb's is excellent.

Switching to the Japanese audio helps in some scenes. Minfilia's Japanese voice actor is better than her English voice actor, but Yda and Papalymo are annoying in either language. I like Merlwyb better in English.