Now the API is at least consistent on the DH part where we have dh_export_key() and dh_set_key() with the same signature. DSA still misses that part, but I also don't know if that's really relevant.

DSA still misses that part, but I also don't know if that's really relevant.

You mean missing dsa_export_key()? Well, it would be consistent, but I personally do not need it at the moment. The dsa_set_key() I use in my perl bindings when importing DSA keys in SSH format (first I extract the raw values which I pass later to dsa_set_key).