I would argue that there's not enough people using Clark. As for me I always keep a charge ready if they try to Hadou me, his EX is really good at blowing up zoning. As for air-to-air I think short hop B and neutral D are good against Beni, Kyo, Iori, and Billy. If they're being really aggressive and jumping in, he has the tools to get them off, his st.A is good for that, st.C and A Gatling can do it at certain distances too.
The game is young, but I reject that's he's relatively low because of some bad matchups.