How did you optimize that ? My WU is about 90% after 5 days of mining on all my rigs, and they all have different settings as they have different cards. 280x are with 13 intensity but they still have 90% WU, 290's are with 20 intensity and high thread concurrency and have again the same WU ( 90% of the hashrate ). So even after a very long period of time ( 5+ days each rig is running with no disconnects or power loss ) i can no get more then 90% WU, in the same time it seems it is pretty much stable around that number for all rigs i have.