Would it be possible to build a purge only
content-type: "text/html" feature into CloudFlare? This might help CloudFlare prevent unnecessarily purging larger static files like images. Images could also be optimized by CloudFlare which takes some time to rebuild if purge everything is used.
Usually if we make a global change to the WordPress template we only need to purge the text/html pages. Purging the static images, CSS & JS is mostly never needed. Even if the static resources do change, the developers can use query sting parameters as cache busters.