Rails app on big machine only gets 60 requests/sec benchmark results
I suspect one of your big issues is https.
I've just run some comparison benchmarks and for me they are showing a 2-4 times speed decrease on a really basic page like that. Do your metrics increase if you hit an HTTP page?
Also check your passenger status (rvmsudo passenger-status) to check that all the processes are loaded and getting requests distributed among them evenly.