The problems with most methods to counter bots is that they are overcome through zerg waves of automatons.
In the event that these are not hacked accounts, then changing the terms of service to include massive charges to anyone that does this would be very effective at removing the profitability. The fees could be structured to greatly increase if the bots are for business(advertising, selling, etc) and could be used to reward the ESO community that has endured this annoyance and obstruction of service.
In the event, that most of these accounts are hacked, Zenimax should utilize additional hardware security methods such as FABs.