My participation in this game is purely voluntary and I'm not out to break anyone's eggs (or more delicate boy parts), but come on!!!! - "it's quite a gentle acceleration" indeed! This has been stated to be presently part of the working DAIMP Store logic - the more chests you open and gold you spend over the months, the greater your absolute chances of high end item drops?
I don't see it. Perhaps my experience is skewed due to a sampling error of one.
Have the majority of high experienced players noticed this increased drop rate of purple cards after 500,000 gold? 1 million gold? Does platinum count?
Correct, you have insufficient data. Personally I saw a higher influx of high level items, accessories and uniques at around the 100-200 prestige mark (which correlates with gold spent / chests opened, which was about a month or two into the game. I got absolutely no accessories at the beginning, now they're a regular thing.
I entirely get where you are both coming from. That's the difficulty of RNG.
I've probably been more lucky (& Drasca) and Dr.H. less, a situation which a ton more play may reverse or not.
Yet I have noticed a nagging improvement in my purple drops over time, having spent 800,000 earned gold.
The 'gentle acceleration' is judged too gentle overall, hence the review.
If opening chests is an accelerator condition, well I pedantically opened chests and smashed pots.
From my own sample of one, unique stuff eventually dropped and then kept dropping.
(Example to make the point that drops eventually drop, not to elicit hate:)

And for 'best weaponry' it's pretty much the same story,
just Caliban, Blade of Red Birth and Shield of the Emperor, and I'm done (until any further gear in DLC).
A piece of feedback I'd wish to share with the BioWare team, (and I say this as someone supportive of the MP)
is that an acceleration mechanic that is essentially hidden is not a good thing, because it divides the success or
otherwise of players by the gaming play style choices they make that they may be completely unaware of, or just due to blind luck.
For that reason, I'm pleased that this is being talked about now.