I would not know if it is entirely related to the dashboards unless I look at the logs. However since you mentioned that you have 10K virtual machines, the View which filters down your Idle and Highly active virtual machines does analyse the utilization stats for last few days. This might be the reason for the spike.
I would recommend that if you are not using the "CPU Bug: VM Patching" dashboard then you can remove it to optimize the CPU Usage. The views in this dashboard are heavy as they are analysisng all the VMs in your environment.
Hope this helps.
Regards
Sunny