1. Add a contribution system... well not all is trying to spawn the same thing, but let it record so as if you do content killing mobs to help doing something you will be able to get XP/Light/Reward from fate, if you afk doing no offensive defensive actions... you would get like 10% XP and no rewards or crystals, as in gotta have an activity log... and if you stop doing stuff combat wise... it will fade out in 3-5 minutes and you would lose your chance to gain rewards from fate untill you start doing stuff again, of course a 10-15min CD when just entered instance of course, no need to punish newly entered and motivated players.
2. Mobs will run to AFK people or people not flagged for having done any stuff, and kill them more freequently... after 3 deaths same area not been recorded for any activity combat wise.. kick from instance.