It’s still per client, but the difference now vs. before is that you can no longer use broadcasting software or hardware to control the clients simultaneously. You have to manually control each one in every aspect of the game. The only “automation” they allow with regard to multiboxing is using /follow on the slave clients and using the master client’s character as the lead.
Farming isn’t a violation of any of the rules. Botting is, but not manual farming. I’ve been doing lots of herb gathering on my second hunter to level up to 60, as that’s actually faster for me than questing is. If you report legitimate players often enough, you’ll get flagged yourself by the GM and could land an unexpected (but warranted) suspension for disrupting others’ activities. Of course with me it’s fairly easy to tell I’m not a bot - I’ll actually strafe out of aggro range of any mob I see, that is if I see them in time (I’m blind in one eye).
Us disabled folks would like a word with you…