I spend a lot of time talking about gear. In the past, I've made loot lists for upcoming content, wrote a guide to enhance stats in Cataclysm, and devoted an entire post to talking about why haste is such a terrible, terrible stat for us. Gear is our only physical (as much as pixels on a screen can be physical) reminder of the boss we killed, and it's the only way for our characters to grow once they meet max level.
In my talks about gear, I've paid a lot of attention to how horrible haste is. Unfortunately, while I've mentioned in brief tidbits that mastery is our best secondary stat, the hot fudge on the ice cream sundae of our gearing, I've gone into little detail on why it's so good. Even worse, I've totally neglected discussion critical hit rating and why it isn't as good. To fully understand enhancement gearing, this is stuff you need to know.
What is a critical hit?
If you've played World of Warcraft to level 85, you've definitely seen critical hits happen before. Your critical strike rating and agility determine your chance to get a critical strike with your melee attacks, which hit for 200% (or double) normal damage. Your critical strike rating and intellect determine your chance to crit with spell attacks, which baseline hit for 150% damage. Caster classes generally crit for 200% on spells, and the fact that we do not despite half of our damage using the spell critical hit table is one of the many things devaluing critical hits for us.
Every time you hit an attack ability or auto-attack, the game's servers generate a table for your attack roll. On this table, you have every possible outcome for your attack: a dodge, a parry, a block, a glancing blow, a critical hit, a normal hit, or a miss. By attacking from behind, we eliminate dodges and parries from the table. Special attacks (also referred to as yellow damage) -- Windfury/Stormstrike/Lava Lash, in our case -- can't be glancing blows, and so glancing blows are off the table. A 541 expertise rating eliminates a boss's normal 6.5% chance to dodge, while 961 hit rating gets rid of your chance to miss on special attacks.
As a result, once we're melee special hit-capped and expertise-capped, our special attacks only have two options: hit or critically hit. If you look at my character sheet, I have just about a 25% chance to critically hit on a melee strike. Taken at face value, it's easy to assume that I'll critically hit 25% of the time if no buffs or debuffs are applied.
Why crit can be bad
Unfortunately, that's now how probability works, and this is part of the reason crit is a bad stat for us. A 25% chance to crit means that every attack has a 25% chance to crit and a 75% chance to not crit. Every melee special ability you use is like rolling a four-sided die and hoping it doesn't land on 1, 2 or 3 every single swing. A 25% chance to critically hit can result in you actually critically hitting 35% of the time or 15% of the time, and thus, it is an unreliable DPS stat.
Longer fights help to mitigate this problem with critical hits, as lucky (or unlucky) streaks don't tend to last for 10 minutes, which is also one of the many reasons programs like EnhSim simulate fights over 1,000+ hours. If you roll a four-sided dice four times, it's much more likely that you'll get fours on every roll than if you rolled the same dice 4,000 times. If you roll it 4,000 times, the chance of your rolling a four every time is significantly smaller. With critical hits, it's the same thing; the longer the fight (and the more rolls to crit you make), you're less likely to be terribly effected by lucky and unlucky streaks.
On the other hand from crit, mastery is an incredibly boring stat. Enhanced Elements, our mastery, is a flat percentage damage boost to all of our attacks that do non-physical damage. This is Lava Lash, Lightning Bolt, Lightning Shield, both Shocks, Searing Totem, Flametongue procs, and Unleash Flame. Stormstrike, regular melee auto-attacks, Windfury, and Unleashed Wind are our only damage not effected by our mastery, which means that around 55% of our damage is increased by mastery.
What makes mastery better?
Because mastery rating is a percentage damage increase, there's no variance in the amount of damage it gives from fight to fight. If you have 2,100 mastery rating -- which equates to a 50% elemental damage increase -- your Lightning Bolts, Shocks, and other elemental damage will all do 50% more damage. This doesn't totally rid ourselves of variance in our DPS, as nearly every spell in the game has a base damage range that forces some element of random number generating into our DPS, and critical strikes do still exist even when fully geared for mastery, but it certainly helps limit our DPS variance.
To compare critical strike rating to mastery on a standstill fight like Baleroc, think of them as two fresh college graduates striking out on their own and trying to make money for the first time. The first kid, critical strike rating, decides to take his life savings and go to Las Vegas and play the slot machines. The second finds a job making $30,000 a year. The first kid has the potential for a big payoff or a huge loss. The second one is not going to be a millionaire anytime soon, but he has a sustained income and doesn't have to worry about moving back in with mom and dad because he blew it.
Critical hit rating gives you a chance at being a rock star on the DPS meters once in a while, while mastery will help to keep you consistent in your ranking on every fight but makes it less likely for you to have a breakout performance where you top every other DPS in your raid by a stellar amount.
Show your totemic mastery by reading Totem Talk: Enhancement every week. We've got enhancement-specific advice on the latest gear and tier gear set bonuses, and we'll help you dig in and learn to level the enhancement way.