When I was a young shaman, wielding my Vanir's Right Fist of Brutality with pride, I gemmed strength. Bold Crimson Spinels were the order of the expansion, because every point of strength was worth two points of attack power and scaled with Blessing of Kings. Agility gave us absolutely no attack power but did contribute to our melee critical chance. With no attack power gems in existence, Bold strength gems were placed in every available gem slot ever.
Wrath of the Lich King saw a change in our gemming strategy. Out went our plate-wearer style stat formulas; in came agility gear! One agility became equal to one attack power and a small amount of melee crit, while one strength gave us just one attack power. Unfortunately, we still didn't get nearly enough of a bonus from our agility. Attack power gems gave twice the attack power of an equivalent agility gem, and the extra crit wasn't enough to make up for an extra 20 attack power. Later on in the expansion, haste was such a brokenly good stat for us that it eclipsed even attack power. Agility spent a second expansion playing second string.
Now, Cataclysm is here, and it is finally agility's turn to shine. Much like the past two expansions, enhancement shaman gearing in Cataclysm is a very strange beast. This post is here to explain what each stat does for enhancement and where it's valued when you're gearing.
Agility is the star player of enhancement shaman gearing in Cataclysm. If your stats were all cast members of The Breakfast Club, agility would be Molly Ringwald. Agility gives us two points of attack power for each point of agility, and it scales with the 5% stat bonus afforded by Blessing of Kings and Mark of the Wild. Additionally, you get 1% melee crit for approximately every 262 agility. Agility is beyond our best stat.
The unfortunate thing about agility is that you can't reforge into it. It's so far and above the other stats that this would be drastically overpowered. Since you can't reforge into it but you can reforge into other needed stats, agility takes priority for gemming. You can reforge all of your other gear to reach needed caps, so you want to save every one of your gem slots for use with a +40 agility gem. As Agile Shadowspirit Diamond requires three red gems to activate, there is no real reason to go outside of the red gemming scheme other than for an excellent yellow socket bonus (where 20 agi/20 mastery is worthwhile).
Even beyond basic gemming, you want to be looking to fill up your enchants with as many agility enchants as possible. While it's fine to use Precision to boots or bracers to reach your hit cap, those are some of the first enchants you want to look at getting rid of. Hit your epic bracers with the costly +50 agility whenever you have the resources available to do it. Throw on an Enchant Boots- Major Agility as soon as you can maintain 1,742 hit rating without hit rating on your boots. Agility is your friend; use it liberally.
Hit rating is different. There are a number of different hit rating caps, some of which you need to worry about and some of which you have no concern for. First off is the "yellow" hit cap. This caps our special attacks, Lava Lash, Windfury, and Stormstrike. You reach this cap by having 8% melee hit. Since being specced enhancement gives us 6% hit rating while dual wielding, we only need 2% melee hit to cap specials. This is only 240 hit rating, and it's the first thing you will cap.
The more important hit rating to cap is the spell hit cap. Every boss has a built in 17% chance for spells to miss them, which we want to see brought down to zero. Unleash Elements, our Shock spells, Lightning Bolt, and Searing Totem all work off spell hit, as does the always important Wind Shear. You don't want any of these abilities to miss, which is why spell hit is the second most important thing for us to cap. We currently have no spell hit talents like a retribution paladin's Sheath of Light. As a result, we want to reforge and enchant into the full 1,742 rating. Do your best not to gem hit unless you're extremely close to capping and can't reforge anything else in.
Finally, we have the "white" hit cap. This is the cap for your auto-attack damage. Auto-attacking makes up a really low portion of your DPS, between 20-25%. It's never a good idea to try and cap your white hits, as the hit rating required would do more good as another stat. The dual wield hit cap is 27%, and we get 6% through talents. You'd need 2,520 hit rating to cap white hits, and that extra 800 hit could all go towards more desirable stats.
Please note, these numbers are relevant for all non-draenei. Draenei need 120 hit rating for specials, 1,640 for spells, and 2,400 for dual wield white hit.
Expertise is the third most important stat on our list. Expertise reduces the chance for the boss to dodge or parry our attacks. Bosses have an intrinsic 14% chance to parry attacks, but that chance to parry is entirely removed by attacking them from behind. Specific fights like Pit Lord Argaloth make this impossible, but we don't gear around specific fights. Since you're attacking from behind, you only worry about the boss dodging your attacks. They have a 6.5% chance to dodge, which is removed by having 26 expertise. This is 451 rating if you're playing a dwarf with maces or an orc with axes or fists. If you're playing a cool race like a tauren, you need 541.
Mastery is your bread-and-butter secondary stat. 179 mastery rating gives us 1 point of mastery, and every 1 mastery gives us a 2.5% increase in fire, frost, and nature damage. Instead of listing everything that our mastery effects that we use, I'll just list what doesn't get affected: Windfury procs, Stormstrike, and white hits. Together, these make up about 35% of your damage, meaning that 65% of your damage is effected by mastery. Additionally, the flat increase nature of mastery means there is no random number generator tomfoolery like critical strike rating. It is simply damage added to nearly every attack
This makes our mastery incredibly good and something you really want to look for on items. Ideally, you want to try and find items like the Treads of Malorne, itemized with mastery and hit rating. Items like those boots are so good that you don't need to touch them with a reforger unless you're slightly over hit cap and need expertise. Mastery is your last choice to reforge out of and your first choice to reforge into once your caps are met. If you have any non-reforged crit or haste on your gear and you're capped with expertise and hit, make them mastery.
Critical hit and haste
Critical hit and haste are both really bad stats. Haste was king when our damage was dependent on white attacks, but changes like the Static Shock change that made it activate on button presses makes haste less desirable. There simply isn't enough benefit to increasing our attack speed when compared to a flat damage increase like mastery. Mastery's flat increase is also one of the contributing factors to crit's poor showing, as critical hit is dependent on RNG and only increases the damage of some attacks.
You won't be able to get gear without either of these on them, but you want to reforge them into something ASAP. Most importantly, don't go for critical hit/haste items like the Voltage Source Chestguard or Arion's Crown. These are largely worthless and would do better with a hunter friend.
Show your totemic mastery by reading Totem Talk: Enhancement every week. We've got enhancement-specific advice on rep gear, heroic gear, and raiding gear, plus tips on maximizing your utility skills and tactics for raiding Blackwing Descent.