It seems to be the case, with players reporting that the sequel might even have imported the anti-farm code from the original Guild Wars.
Guild Wars has a little known but well-documented anti-farm code which is basically a bunch of programming scripts designed to "reduce the benefits of repeatedly farming a single location, quest, or other objective."
Guild Wars anti-farm code was implemented sometime in 2007 to thwart the huge influx of gold that professional solo farmers were earning and pumping into the economy. The main method ArenaNet used is a loot scaling system which essentially nerfed gold and common item drops for dedicated solo farmers.
Fast forward five years later to today and Guild Wars 2 players are noticing that the same anti-farming measures are in place in the newly launched MMO. Some speculate this is to impede Guild Wars 2 digital cash farmers who are engaging in RMT. But it is also hurting a lot of non-RMT gamers who are farming for crafting materials.
GameFAQs user MW3_Fan said that he "hit a brick wall with their anti-farming software. I'm not allowed to farm materials now? Been in the Norn starting area trying to farm cloth but after awhile it shuts me down and nothing, just a waste of time."
Meanwhile, GuildWars2Gure user Fahrar Cub said that his attempt to farm the same mobs over and over again was thwarted. "After farming for 30 minutes and having your loot just completely dry up, especially in Orr since everything is undead just seems a little bit much, especially when crafting is using as much materials as they do."
And over at the Guild Wars 2 official support forums, user Healerith said that the anti-farm code does exist for Fine crafting materials, a class of harder-to-get ingredients for crafting. "The way it works is basically like this," he says in describing the ant-farm code, "Let's say you farm spiders for 1 to 2 hours for venom. You get some decent drops that first hour but then you may only get 1-2 venom the entire second hour."
"When your drop rate goes from low to non-existent you have hit the anti-farm code."
The anti-farm code also seems to cover dynamic events, so that running them repeatedly will yield less gold and Karma rewards each consecutive attempt. Also, to prevent no-effort farming, dynamic events are programmed to limit the rewards of players who do not perform actions related to the event within a period of time.
Since ArenaNet has not and will probably never reveal the exact rules behind its suspected Guild Wars 2 anti-farm code - for good reason because revealing so would only undermine its design - players have brought up possible solutions.
Guild Wars 2 official forums user Healerith proposes that farmers "pick another area and type of mob that drops the same fine material and farm them for awhile instead" suggesting that breaking up your farming routine, widening your farming area and alternating between farming targets could get around the anti-farming code.
Does Guild Wars 2 Have an Anti-Farm Code?
By Frank Lewis, Sep 17, 2012