If you're going to complain that a champion is no longer unique because they are part of a new race.
Then they never really were unique in the first place. At least not in a good way.
A character should be defined by their actions and personality more than their race. Race can be used as a good tool, but it isn't something that you can use to fully support a great character.
Ahri and Nidalee being Vastaya (and I don't believe Nid is one but whatever) actually gives the writers more room to make them unique. Rather than just making Nidalee "magical for no reason Tarzan" or Ahri "generic fox girl number 1642"
Did they have unique traits before? Yeah (at least Ahri did), traits that people seem to ignore. Ahri's character arc is about the struggle to become more human in both body and spirit. She was a monster that wanted to be human, something that we don't really see in other "monster" champions.
I'm probably going off on a rant here, point being that being in the same racial group doesn't stop a character from being "special" and being "special" because you're the only one is a poor character concept (something that teenage anime fans have to learn eventually. We all do).
Hell, even Alistar and Skarner aren't just about being the only ones of their kind left! Alistar is about his own pride costing his tribe's safety and Skarner is about rescuing his people. Race is important to them, but it's not what they are that defines them. It is what they do.