Yes...You don't calculate efficiency with mW per Ma.
It is Mw per Mw. Power in versus power out.
CO2 lasers can be up to 25-30%.
Some commercial diodes can be up to 60%.
I read some in the lab are up to 76% with a goal of 80%
All these are in the IR range though.
Also keep in mind the driver efficiency!
Here is the source I got the info from.