Take Mark of the Wild for example, which gives 54 resistance to all schools of magic.
This is important information to know when thinking about Spell Penetration. For example, at level 80, 82 spell resistance does absolutely nothing, but 83 negates 15%. However, Magic Resistance works on a table, with tiers that determine how much of a spell is resisted. Spell Penetration negates spell resistances Point for Point.
As stated, it is mainly a PvP stat designed to negate the effects of resistance buffs like Mark of the Wild, Prayer of Shadow Protection, etc. Spell Penetration has absolutely nothing to do with Spell Hit Rating, and only applies versus targets with Magic Resistances. Most players will never even think about Spell Penetration, and it is argued it’s very limited usage is really only for PvP. Spell Penetration is a weird stat because of how uncommon and situational it is. It is hard to say just how much spellpower a level 80 player “needs” because it varies a bit, but 2000 is typically considered “decent” for most classes - but you should always strive for more. This is considered to be the most important stat for all classes that cast spells - Warlocks, Mages, Priests, Holy Paladins, Restoration and Balance Druids, and Restoration and Elemental Shamans. Spellpower is not derived from any stats, but rather is found in a flat amount on all caster gear and items. Every ability will take a percentage of a player’s spellpower and modify its ultimate effect by that amount. Spellpower is the stat that modifies how much damage or healing any caster’s spells will have. It is less useful for Frost and Unholy Death Knights because much of their damage is magic based, whereas Blood Death Knights need ArP because they’re mostly physical damage. Of course, Armor Penetration is only useful for physical damage classes like Rogues, Hunters, DPS Warriors, Death Knights, Paladins, Feral Druids, and Enhancement Shamans. In other words, 12.31 Armor Penetration Rating directly converts into 1% of ignored armor at level 80.
More important, though, is the amount of Armor Penetration Rating required to ignore 1% of a target’s armor, and that value is 12.31:1. Armor Penetration Rating converts into Armor Penetration Points at the rate of about 7:1. Armor PenetrationĪrmor Penetration is a value often found on Leather and Mail gear that gives the player the ability to “pierce” a percentage of the target’s Armor. Typically, players will prefer the pure stats (Agility and/or Strength) over AP because those stats scale with buffs, like Blessing of Kings. Attack Power effects ranged and melee physical damage, and is directly responsible for damage scaling on attacks. It is, however, also found as is in high amounts on Leather and Mail armor, as well as “generic” pieces like Rings, Necklaces, Weapons, and Cloaks. Attack Power is a derivative stat, meaning that most Attack Power is directly derived from Strength or Agility, depending on the class.