Hmmm, I have seen YouTube videos where Gale pronounces metamorPHOsis, which is what I recall from my game experience, but there was one video clip where he says cereMORphosis. Curious! Maybe it was a response along a different dialog tree. So, I guess learned Gale goes both ways.
There are other pronounciations which I found odd:
1) Myrkul would sound better to me if pronounced as mere-COOL, but instead we usually get something sounding like Angela Merkel's last name. Ugh.
2) Abdirak has a great set of voiced lines, dear ones, but I do not like Love-EE-atar as much as I would prefer Love-EYE-atar.
3) Everyone in the game says ZHENtarim, but I think it would sound more exotic if pronounced zhenTARim.