I'm not sure how long these have been around, I personally noticed the first one like two or three weeks ago in Coerthas, but now with the release of Rogue/Ninja these bots became a lot more common.
How do you know that's a bot?
After the 2.28 update players are no longer able to move around the map with the AFK icon, performing any action removes the afk status regardless if it was set manually or automatically.
These bots, just like those miner bots, are able to travel around the map attacking only fate monsters, though they tend to get stuck when they walk into a platform.
Are these bots also going to be ignored by the Special Task Force / SE?