Workload is not related to Usage. Usage is mapped to Consumed. Usage is mapped to Active at VM level, but to Consumed as ESXi level.
Workload is based Machine Demand. I'm not 100% sure what the formula for Machine Demand is. It contains Active as the pattern is similar, but definitely not just Active as the value is _always_ higher. I'm using vC Ops 5.8.1 and I checked on a few ESXi 5.5.
Hope that helps
e1