Multisite Slowness — Early Blog ids fast, higher blog ids 10x slower

I have a multi site running approximately 150 sites on WP ver 4.7.3 with PHP 5.6.34 x64 and Apache 2.4.29 x64 and MySQL 5.6.3x (forget which).

With Apache Benchmark, blog id 1 gets between 150 and 250 requests a second while blog id 189 gets between 18 and 20 requests a second. In fact, nothing after the first site gets more than 30 requests a second. Neither my main front end nor my db are regularly running at more than 50% cpu/RAM capacity, so it doesn’t feel like load issue per se.

Could this a problem with mod_rewrite? My .htaccess is pretty standard with one exception so that the site can work behind a load balancer.

We’ve recently began going through the exercise of disabling and re-enabling all of our plugins one at a time (there are about 58 across the network), but given the load times we are currently getting I don’t know that we have the bandwidth to completely test this across 150+ sites.

I have wp-supercache enabled and am also checking wp-query monitor for slow queries.

A couple possibly relevant things, my network cannot talk to the internet via HTTP and security settings often block client side calls to CDNS. To to the nature of the installation, some of the items are out of date, but since I can get 150 to 200+ requests a second on one part but not others this feels like either an .htaccess or Apache issue to me.