There is a server-side version of MathJax: https://github.com/mathjax/MathJax-node. This server-side version only processes a formula once, after it is submitted to the server. The server can then serve the compiled version (i.e., an HTML file with a CSS style) to the user agent, which can then render the entire page almost instantly, compared to what it takes the client-side MathJax to render it.
Such a setup seems to be much superior to the current situation. Would it be possible to adjust the software accordingly?
Added 2018–3–11: The new version of MathJax-node seems to have full support for the HTML+CSS output. In light of this development, can we now revisit the question of switching to the server-side MathJax?