I get the feeling that the devs are reaching for the easy button here to make for a more balanced game experience. Wouldn't a better solution be to design the encounter around the abilities of the expected participants rather than nerf one of the participants based on the perceived imbalance that a poor design created? Why not raise the saves on hard and elite epic level mobs to a point at which instant death spells would be difficult to achieve without debuffing the mobs first? Require arcanes to expend more spell points per wail so that their pool shrinks and they NEED the other characters to complete rather than forcing them to sit in a quest, waiting for their timers to clear. While this might be unfair to lesser geared characters, what are they doing trying to run content for which they are unprepared anyway?
With this mechanic I'll be farming the epics the same as always, just getting a cup of coffee between wails as I wait for the timer. This doesn't seem like an effective way to balance the quest to me.