Well that only added more mystery to the rates since mods and admins keep saying 8k is cap but in the video he clearly says that a 10k pointer has higher chance than the 7k ones. I mean we would have to know at least something about the points and how it affects the rate.
There are alot of opinions going around but some facts would be nice.
From what I recall, in a solo anything past 8,000 points doesn't impact the chance of a purple. The limit goes up based on group size, although I don't know the exact numbers. For example, if you're in a duo, the limit might be 9,000 points, in a 5-scale it might be 11,000 points and so on.
If you're wondering why there's a cap on points in the first place, I believe the limit was set because you used to be able to abuse a bug to gather large amounts of points and get like 7 purples in 1 raid(but don't quote me on this).
As for the drop rate, only Omicron can confirm it, but if I had to guess then the drop rate with no donator rank/any boosts is like 1 purple every 150k points. On my ironman I was getting a purple every 10 raids while getting 8,000 points in solo's, having master donator rank, using both raid/drop boosters, and doing it during the Chambers of Xeric 1.2x boost.
On my main I was getting a purple every 5.5 raids with the same boosts as above, so it's hard to tell.