I've heard Yoshida mention in a few interviews that the similarities were not intentional in his character designs.

I prefer Amano over nomura as well. Amano always had interesting monster designs and his characters were always gorgeous. When I saw the opening to FFVI in FF Anthology my jaw dropped at how well his designs worked for the scenes. It's a shame that we have finally reached a technological level that would allow SE to properly convey his artwork and he no longer works as a character designer...

I feel the real problem with the games that Nomura has worked on is the fact that they tend to have the common theme of being potentially good. His games have several wonderful ideas to work with and yet they never use any of them well or just completely drop them, making them irrelevant. The GF's taking your memories from FFVIII, the entire concept of the Nobodies, Roxas' role, the list goes on...