Almost every single online game that has a market will have currency sellers, if there's a crafting/gathering side to it, you will find bots. So unless you get every single game (some which don't have the staff to do so) to get rid of every single bot, and put in counter measures to prevent them from coming back it's literally impossible to get rid of bots. Even then when you put in counter measures, they find a way to get past them. It's no different from DDOS, Hacks, Scams, Fraud, etc.

I remember when I got tells from the gil sellers all the time, haven't had a gil seller send a tell to me since i've been back in the game, so them getting banned in waves is probably having an affect it's just very long term.