It's almost always a bad idea to use anything other than a non-blocking/async server to handle static content.
I think it's simpler/easier (maybe faster) to serve content from a separate sub-domain (static.site.com or whatever). Using a reverse proxy works too, but unless you're caching dynamic content it's probably no benefit and it's less efficient.
A good reverse proxy will buffer client and server side so that your heavy app can be available to serve the next request whilst the light proxy feeds the page back to a slow client.
Under certain circumstances serving static files from separate hostnames can be beneficial as HTTP clients are supposed to limit the number of simultaneous connections per hostname.
I think it's simpler/easier (maybe faster) to serve content from a separate sub-domain (static.site.com or whatever). Using a reverse proxy works too, but unless you're caching dynamic content it's probably no benefit and it's less efficient.