As you know, a lot of buffs and debuffs were changed dramatically in 4.0.1. Categories of buffs were merged, buffs were strengthened and weakened to match each other, all that good nonsense.
Among the buff types that were completely changed were the AP debuff, which previously removed all or nearly all bonus attack power from a boss, and the -3% damage taken buff, which belonged to a couple healers and (at the time) a prot warrior’s Vigilance. The interesting thing to me was that they were changed into identical effects: 10% physical damage reduction. They were implemented in different ways – one as a debuff (-10% physical damage done by the mob) and one as a buff (-10% physical damage received by the player) – but given the amount of buff consolidation that was going on at the time I wondered if they would still stack.
Nobody else seemed to wonder. I guess I’m either really slow or a lateral thinker. Or a really slow lateral thinker.