Can I suggest turn on SPDY as a 5th item, which meets the "low effort, big impact" goals. I started another thread about it here:
https://moodle.org/mod/forum/discuss.php?d=231445
If anyone's already doing this reporting back to the community so this can become a recognized best practice for Moodle could speed up a lot of Moodles.
Hardware and performance
3 things to do to enhance speed.
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