Highest score when? 

Ever? Maybe over a rolling average of 3-4?

I don't like highest score.  That would be unduly punishing for one-offs.  Example: I regularly do 350k-400K for PR CVCs, and 250K-300K for non-PR CVCs, but I did 800K on a PR CVC one time.  I should not be tied to that 800K forever.     

A 4 week (or even 6 week) rolling average fixes the tanking without creating other problems.  I have suggested this exact solution via Discord a few times.

I was thinking somewhere between the last 4 or up to a year, allowing for a reset if there's a major change to mechanics or scoring, like with hydra

Any kind of average will be manipulated lol.  Max of last 5 to 10 works, could even throw out the highest if u did 10

Well, literally no system is as easy to manipulate as the current system of the last non-PR CVC dictates your tier placement & matchmaking for the next PR CVC.

It really begs the two-part question:  Are the Plarium Devs really that clueless? Or did they intentionally design it to be manipulated?

personally i think the present system works fine, i aim at 400k every PR CvC then see how it goes as to wheather i need more points to try and win, during non PR C vC i aim for as little as poss usually 100-150k, when ever there is back to back PR CvC thats what causes stess and point inflation, last time they did it i ended up with 750k points, point being i can cope with once a month  burning res for it more than that wud lead to burn out fast, or worse from Plariums point of view indifference to CvC

Just get rid of the have to win to get personal rewards. It encourages bad behavior.  

It encourages spending, it's not going anywhere