I think, the following might just work fine:
<Metric attrkey="cpu|vcpus_to_cores_allocation_ratio" label="vCPU to Core" unit="1" yellow="5" orange="6" red="7"/>
which resourcekind are you using? And which version of vrealize operations manager?
Just an FYI from 6.7 on-words you dont need to create metric config files for charts, scoreboards etc anymore. They added a mode object types directly in the widget config
which is great as i can now get the CPU usage for every VM in a group with the addition of the relationship option as well. I was only after that for 4 years
Just found out because i tried to do it. You still need a metric config for properties