I also have /i available to be served locally, but I found APEX is passing some parameters on to some of the static resources, which Apache doesn't much care for with static resources.
I'm experiencing some significant delays when running it, however. When I access /apex, I'm 302 redirected to /apex/apex. That redirect takes a few seconds to be sent back to my browser. /apex/apex then takes about twice as long to redirect me to f?p=4550..... which returns a 200 and data in about three seconds. Additional resources are loaded in miliseconds.
In my testing, when I hit the backend DB directory, I'm finding these initial redirects generally take a few ms instead of several seconds. It is pretty regularly repeatable. Any thoughts as to why the Apache proxy would introduce so much delay?
Typically, serving static content via Apacha (as Jari mentioned) and some tweaks of the shared server parameters give quite acceptable performance if the load is not too heavy. However, you should investigate switching to Apex Listener or OHS / mod_plsql, if security and scaling is an issue.