How do I assess how "normal" my battery is?
Yes, you are going about this the right way to determine your battery's remaining capacity and life. 

When a battery reaches over 1000 charge cycles, it is considered "consumed", aka it's lived out the expected life cycle and any degradation in capacity is totally expected. This is never covered by warranty. A consumed battery may still hold some charge, and in some cases a lot of charge, though that is rare. 

A battery would be deemed "failed" and OS X would report it if it holds less than 80% of its factory full charge capacity. If this would happen within the first year, then it would be covered by warranty. This is the way OS X and diagnostics determine the health of the battery when the complaint/concern is poor battery life. 

The battery Can also unexpectedly fail if the thermal sensor in the battery goes bad. But this is something that's impossible to preventively pick up with software.