I pretty much agree with pretty much everything in your post but I've highlighted the main points.
I did at least 200 Olga kills during the event, hunting without any dark weapon - although it was very rare to do a run where nobody had a dark weapon, so runs usually went pretty quickly. I didn't manage to find a PGF (although I saw a few drop and managed to get a pd - which almost destroyed my controller!) but I have to say, as frustrating as it is not getting a PGF, the worst part is having nothing to show for all my effort.
Surely it could be implemented that Olga always drops a green box stackable ticket that can be exchanged for something? If not, some way of rewarding a lot of effort.
I also like your idea of scaling drop rates based on amount of runs or amount of pgf's found ie. once you've found one, it's a lot harder to get a second - although I guess that would be extremely difficult to implement.
Personally I would love to see PGF huntable all year round with a low drop rate, increasing for the xmas event. This would help lower the crazy prices that are going around right now, which in my opinion is terrible for the economy. As you say, someone finds two or three PGFS and they're super rich and can buy every item they like. One spare PGF and you got 300 dts to blow, which pushes the prices of everything else up. For an item that is actually quite common (about 90% of the people I play with have at least one dark weapon) the price is insane.
I'm not one of those that constantly moans and threatens to quit (I'm looking forward to the valentines event!) but it's a situation that needs to be improved. However, thinking about it, most people who wanted a PGF found at least one, so it only affects a few of us and I guess most don't care.
I'm not sure how much attention @Larva pays to posts like this, especially from relative new comers to the server but I'd love to know his thoughts.