I felt Rene Auberjonois and Armin Shimerman both got better as their makeup improved. I think Nana Visitor was better as she toned down her anger, but in her defense that was a character development.
Kira's development became obvious after Duet: confront past, grow mature. Odo's was more difficult. Auberjonois was extremely disappointed with his character in season one. He may have even threatened to quit. Season 2 was a huge turn around, obviously leading into the cultivation of the Dominion War. In the beginning, he was the funny alien who changed shapes. By the end, he held the key to understanding between peoples: he was the one who brought the Dominion War to its end.