Hi, I'm new to these forums. Inner Demons are vulnerable to Arcane, Nature and Holy damage, and resistant to Frost, Fire and Shadow. They have roughly 12,000 health and need to be killed in 25 seconds. Targets are chosen randomly, but I think the highest-aggro is excluded.
At first glance, it seems like they are impossible for healers to kill. However, Druids use Nature and Arcane damage, Priests use Holy, Shamans use Nature, and Paladins use Holy. Again, Inner Demons are vulnerably to these elements, while resistant to all others. This is probably why this fight was designed this way.
From my experience, the classes who have the most difficulty killing these are Restoration Shamans and Protection Warriors, and to a lesser extent, Hunters and Holy Priests. There are countermeasures to ensure that these classes can beat their demons. I'm sure most of you can figure it out for yourselves
