Myself and countless others on the server lost all progress and were literally unable to proceed beyond spawn due to a hacker blatantly killing anyone and everyone regardless of where they were on the map.

See video here: https://streamable.com/ehue8b

Earlier this week something similar happened, and I naively thought it must be a rare occurrence, so my friend and I changed to a different server and started again. Are we supposed to continue spending hours upon hours building our characters up again just hoping the same thing doesn't keep happening, when it's obvious nothing is being done about it by the only people in the position to fix it?

It is completely absurd that such blatant incidents can't be detected and acted upon automatically/programmatically - all it would take is a simple script parsing the logs and watching for known anomalies. These incidents are so obvious that a false positive would be unimaginable.