i have experienced high cpu (i3) usage 100% when mining on 4x 1070
Nvidia's OpenCL drives implement busy waiting which leads to 100% core utilization per instance. I have changes that work on Linux,
https://github.com/mbevand/silentarmy/pull/60 I don't know what is status of them being ported to Windows.
My Windows port includes a modified version of your patch, which seems to be working fine.