With an RX 480 Sapphire Nitro+ OC 8gb stock-settings mining XMR I get 645 h/s; I took recommendations from the Eth. board and overclocked memory by 200, reduced Voltage by 48 which resulted in a stable 724 h/s, 'good enough.  Well, perhaps the newest GPUs (Pascal GTX 1000s and Polaris RX 400s) and their drivers are in line for mining software optimization by some crafty programmer.