Consideration should be given to eliminating competition for nodes.
First, allow a character to harvest a node regardless of other players harvesting it.
This will eliminate competition for nodes, making node harvesting bots less profitable. It will decrease the sales of raw materials for both in game and real world cash, because the players who want the mats will be able to go get them. There will still be players who are lazy, but overall demand would go down making mats less profitable for bots.
Second, restrict how often each node can be harvested by each character.
This will encourage more exploration by actual players while making Bot programing more difficult. Bots could no longer infinitely harvest a single zone. If each bot can harvest each node only once a day, each bot would be considerably less profitable.
Furthermore, frustration of actual players would go down considerably, since their mats would not be stolen by a bot hidden underground.
Because of the high skill requirements to make high end goods, I think the economy would remain strong.
This is clearly not a total solution to the bot problem, and anti-bot programming on the server side would still be needed. But decreasing the bot driven angst of your paying customer base can only be a good thing.
Please give this some thought.