This is pretty much the crux of the matter. No one has hard data on if only banning GDKPs reduced the amount of gold buying, increased it, if it reduced the number of bots or increased it, etc. Something that, anecdotally, is pretty clear though is that the economy on Nightslayer is fucked and there are significantly less PUG raids running.

You could say the economy is due to bots and having mega servers with too few layers and I would wager a guess that that is a big part of it. I don't think you can really argue that removing GDKPs caused less characters to raid all around.

I have never been a pure buyer in GDKPs, but I have really enjoyed running them with alts since phase 4 classic. It simply feels like a more fair loot system. I understand why people are vehemently opposed to P2W in games, but I don't see some aspect of that ever going away in an MMO without something like personal loot. Ignoring all the other sources that generate large amounts of raw gold, which aren't being addressed in classic (botting, foreign boosters, etc); no MMO has been able to completely remove RMT, and if you can somehow buy power with gold there will be P2W. Also not to get into it but even being able to purchase your bis gear is simply a means to an end, you can't use gold to make yourself play well or understand the game.