To be fair, they're not actually AFking. They're just being lazy and taking advantage of people doing their work.

If they were truly AFK they would have been kicked out by the instance. I would know because my queues for Frontlines are over 20 min. I had ordered pizza and the delivery had happened just as I had finished securing markets. Came back from the door with the food and the instance had kicked me out. My fault for ordering pizza and wanting to do frontlines at the same time. And immortal flames was winning for once..