Even fresh level 80 characters should survive this:
Lightning Nova
5 sec cast
Emit a pulse of energy that deals 6013 to 6987 Nature damage to enemies within 20 yards.
On Heroic my first try was over after the first nova - 3/5 dead because of the damage and the low health of my toons. :P At least the first time - if you can survive that damage, just cuddle in front of the boss and kill him without a problem.
Lightning Nova
4 sec cast
Emit a pulse of energy that deals 10638 to 12362 Nature damage to enemies within 20 yards.