I'm using asus r9 290. This far these are only good settings I've managed to figure out.  Still little bit of work.
Giving steady 410khash with 0 hw errors and rejects.

{
"pools" : [
   {
      "url" : "",
      "user" : "",
      "pass" : ""
   }
   
]
,
"intensity" : "18",
"vectors" : "1",
"worksize" : "512",
"thread-concurrency" : "24000",
"shaders" : "2048",
"gpu-powertune" : "20",
"gpu-threads" : "1",
"no-pool-disable" : true,
"scrypt-vert" : true,
"kernel-path" : "/usr/local/bin"
}