As someone who makes packs that are usually combat intense, I understand how extremely important Armor Penetration is to making end-game mobs challenging. Armor Penetration is the only way to actually pose a threat to a player who has full Diamond Protection IV and resistance, or modded armors. May I suggest making Armor penetration it's own affix? Maybe beefing it up a little bit? I think it would be great to appear on a lot of end game mobs... but I dont like that it only comes attached to the Molten affix.