Soloing Tomb of Sargeras i have found that there is a 10 Minute DoT applied to the player from the trash mobs before fighting Kil’Jaeden. This DoT ticks upwards increasing in the amount of damage it does and is unable to be removed by most classes unless they have dispel magic abilities.
This DoT does not need to be removed from the game, but i think the 10 Minute timer on it is a bit over the top and it becomes a race to see if you will kill the boss or if the trash mobs DoT will will you. Perhaps a 1 minute or 30 Second timer on the DoT would be a better solution?