You have already considered this and there may be some reason why you don't implement it but I thought just in case you hadn't I would put my ideas down.

How I would approach Gold spammers.

The key is to make it as unprofitable as possible. The key is that they have to advertise. That is there weak point. I am assuming that they have to buy the full client like the rest of us. At £50 that is a considerable outlay.

So closing them down fast means that the cost per advert goes up considerably.

So add an option when you right click on there name to "report gold sales". it should be as simple as that, no follow up questions or form to fill out. When you get a set number of reports from players you close down the comms for that account. That then gets flagged up at the help desk and they make the call. They can then delete the account. If it is legit and Players are taking the *** then the comms can be reinstated, and maybe those player ability to report gold spammer is removed.

Ideas for dealing with bots:-

Same sort of thing, have an interaction option that says report bot. When you get enough reports it forces the person to enter a code (those ones that can't be screen read). repeat offences are reported to the help desk.

other ideas:-
You can only collect loot off bosses once an hour

If you stay in the dungeon for more than a set time hours you are logged out

Xp diminishes the more of one type of creature you kill.