One of my guild mates went through @ 25 potions to finish Normal. Gree, are you kidding? Seems like this happened recently, and you lowered the mobs required
15/15 needs 42 kills x 150energy = 6300 energy.
20/20 Heroic is kill 70 mobs x 205 energy each = 14.350 energy
Guess I'll enjoy a few days off until the war.