Hitting the wayback machine, I was reminded of a bug from the early days of City of Heroes. Damage resistance debuffs also debuffed resistance to damage resistance debuffs. That is, if I hit you with a 30% damage resistance debuff, not only would your resistances drop, but you would have a 30% larger effect from the next damage resistance debuff to hit you. Take Enervating Field, a damage resistance toggle, and have two characters drop it on the same enemy. Tick tick, tick tick, and it is stacking by multiples, not by adding. Some people still have screenshots of doing >10,000 damage in one hit after letting the enemy sit there with several debuffs toggles going for a while.