In this guide I'll be explaining things you need to know when playing a shadow priest, focusing mostly on stuff that's related to raiding, but what you read here could probably be applied to other areas of the game as well. I'll try to keep things as clean and concise as possible, and if you have any more questions/inquires or just something you're not sure of, feel free to ask me and I'll see if I can answer it for you.
1: Gear & Stats
2: Gems & Glyphs
4: Spell Priorities
6: Addons & Macros
8: Useful Links
Gear & Stats
As with all casters, our 3 major stats are spell power, haste rating and critical strike rating. Spirit and Intellect also affect our DPS, just to a lesser extent. Here's a breakdown of the current theoretical value of all stats, normalized to spell power (as of 3.3.5). 1 point of each stat has the theoretical value of:
Spell power = 1 spell power
Critical strike rating = 0.76 spell power
Haste rating = 0.98 spell power
Hit rating = 1.88 spell power (when not hit capped)
Intellect = 0.22 spell power
Spirit = 0.59 spell power
When comparing the quality of two different items, you would use the formula: spell power + crit*0.76 + int*0.22 + spirit*0.59 + haste*0.98 + hit*1.88 + sockets = ? which can be tedious. Sadly, the old calculator that was posted on shadowpriest.com is gone since the site was bought out by another owner and linked with h2priest. As a side note, the current hit cap is 289, which is a number you should be aiming to reach.
Gems & Glyphs
If you can't reach the hit cap through your normal gear, it might be a good idea to gem for hit rating. Other than that, try to fill your red slots with Runed Cardinal Ruby or cheaper versions if you can't afford it. Put Reckless Ametrine in yellow slots and Purified Dreadtone in blue slots if the socket bonus is worth it. A rule of thumb for socket bonuses goes as follows: if the socket bonus yields 7 or more spellpower, gem for it, otherwise, gem straight spellpower. In general, it’s not advisable to gem for hit, so as soon as you’ve gotten some better equipment, you should try to get the hit from items, rather than gems. As for your choice of a meta gem, there's only one real option, and that's the Chaotic Skyflare Diamond which gives +21 Critical Strike Rating & +3% Increased Critical Damage. The meta gem requires you to use two blue gems, so make sure to fill that requirement.
As for glyphs, there are a lot of options for the minor ones, and which ones you use doesn’t really matter. I personally use Glyph of Levitate, Glyph of Fortitude and Glyph of Shadowfiend.
When it comes to major glyphs, we have 4 and we switch between Dispersion and Mind Sear glyph depending on the encounter. Generally, if you're not using Mind Sear in an encounter, you should be using the Dispersion glyph. If you're not doing hard modes, it's not really necessary, but even so, there's some encounters where the dispersion glyph can really come to good use. I'll be doing a separate guide on some tips & tricks to use in ICC and ICC heroic, which you can use to your advantage to maximize your performance. Dispersing at the right times is one of them.
Always: Glyph of Shadow, Glyph of Mind Flay.
Depending on encounter: Glyph of Dispersion, Glyph of Mind Sear.
Alternate Glyph: Glyph of Shadow Word: Pain (if you're having mana issues)
Head: 30 Spell Power 20 Critical Strike Rating (Kirin Tor reputation)
Shoulders: 24 Spell Power, 15 Critical Strike Rating (The Sons of Hodir)
Cloak: 23 Haste Rating
Chest: +10 All Stats
Bracers: +30 Spell Power
Gloves: +28 Spell Power
Pants: 50 Spell Power, 30 Spirit
Boots: Tuskar's Vitality (moving around faster will help you to survive, and in some fights increase your dps substantially) or Icewalker.
Weapon: +63 Spell Power or Black Magic (250 haste rating proc) (1-handers), +81 Spell Power (Staves)
There's also several profession-specific enchants, such as ring-enchants, cloak enchants, shoulder enchants and various other enhancements. Make use of those where applicable.
Shadow priests don't have a set rotation, and instead make use of spell priorities, reading the situation, and planning ahead. With 4-set T10 and meeting certain gear-requirements, our spell priorities will change slightly, but I'll go over the basic spell priority list first.
There are many variations on openers to use, but I recommend this one, which is used for both spell priority sequences:
Vampiric Touch > Devouring Plague > Mind Blast > Mind Flay > Shadow Word: Pain
Normal spell priority (Non 4-set T10)
Vampiric Touch > Devouring Plague > Mind Blast > Shadow Word: Pain > Mind Flay
In other words, make sure to always have Vampiric Touch, Devouring Plague and Shadow Word: Pain up and ticking, while burning Mind Blast on every cooldown. If there's nothing else to do, just Mind Flay, but be sure not to cut off any Mind Flay ticks. If you're in a situation where Mind Blast/Vampiric Touch/DP should be cast after 1.5s, just cast another Mind Flay, even though the target would be without Vampiric Touch for a second.
4-set T10 spell priority
Vampiric Touch > Devouring Plague > Shadow Word: Pain > Mind Flay > (Mind Blast after every VT)
Very similar to the normal spell priority sequence, but with the exception of Mind Blast being semi-dropped. It's important to realize that we're one of the few sources that supply replenishment, so it's still advisable to cast a Mind Blast after each Vampiric Touch to keep it up. This change however, allows us to change our talent spec a bit, which I'll cover later.
The most important thing for both spell priorities is to know your ABC's, Always Be Casting. Stopping for things to come off cooldown or waiting half a second to get perfect uptime on DOT's will only make your DPS suffer. Make sure that you're not unintentionally cutting off your Mind Flay before the last tick, and don't refresh your dots before the last tick. Recasting a Vampiric Touch 0.2s before the last tick is a major damage sink, and really ought to be avoided. With more haste you also have to remember that your casting times get lowered, so even if you usually start refreshing Vampiric Touch when there's 1.3 seconds left, it will be applied much faster with Heroism so pay attention to that.
In encounters with multiple targets, a good shadow priest keeps dots running on all targets simultaneously, or using Mind Sear if the encounter allows it. Additionally, you should only cast Shadow Word: Pain when you have 5/5 stacks of Shadow Weaving, as you will keep rolling this Shadow Word: Pain for the duration of the encounter, unless you refresh it at a later stage. Having applied Shadow Word: Pain with 1/5 Shadow Weaving will lower the damage output of it. Shadow Word: Death should only ever be cast while you're moving. Never use it if you're stationary and DPSing a target.
Threat shouldn't be an issue for shadow priests. When you're about to pull a boss, make sure to fade just before the tank has engaged it, so you can apply dots and mind flay without worrying that you'll pull aggro. These days, with misdirect and a few broken ToTT's on the tank threat should really not be an issue. Fade is a great spell to have at your disposal when you're aoeing, make sure to use it if tanks got low aggro or if you're quick to mind sear freshly spawned/pulled mobs.
List of consumables that are good to bring to a raid:
20x - Flask of the Frost Wyrm
60x - Potion of Wild Magic
60x - Potion of Speed
60x - Tender Shoveltusk Steak (or any +46sp food. Fish feast is used normally though)
Normally, on harder encounters you pre-pot before engaging the boss. Have the tank do a countdown and as soon as it reaches 1, use a Potion of Wild Magic and fade, and do your opening sequence. This will allow your potion cooldown to activate, allowing you to use another potion a minute later. The reason for using a Wild Magic at the start is because the crit rating it provides will stay with your Shadow Word: Pain for as long as you keep it up through Mind Flay. Spell Power on the other hand refreshes on each Mind Flay, so there's no way to abuse that to our advantage.
Further into the fight, you should be using a Potion of Speed to increase your DPS. Make sure not to use it during Heroism, as you'll not be able to make use of all the haste you'll have with that combination.
There are really only two talent-specs that are relevant for PvE. One is the normal cookie-cutter one that most of the shadow priests use, and the other one is the spec tailored for 4-set T10.
Normal talent spec
4-set T10 talent spec
As you can see, the biggest difference between the two is the exclusion of Improved Mind Blast in the T10 spec. This allows for a bit of flexibility in that particular spec, but I've included the most common T10 spec in this guide. It has the very beneficial 2/2 Imp VE talent, which is great to have in hard modes. It also has Inner Focus and 2 points in threat reduction for good measure.
Add ons & Macros
There are two addons that all shadow priests should really have. A good dot-tracker and a good castbar addon. As always, a clean UI is also very important, and I think a lot of people overlook that aspect when making their own UI's. Having an addon to keep track of your DPS can be handy, with Recount and Skada being the standard DPS display addons these days.
Dot trackers: Auracle, ForteXcorcist, ClassTimer, DoTimer.
There are many addons that can track your dots for you, but I personally recommend ForteXcorcist, even though it can be quite annoying to set up.
Casting bars: Quartz, Gnosis, AZCastbars.
Quartz is pretty much the standard these days, so that's what I'm currently using. As long as the castbar shows the latency on the bar so you can properly time your spells, then it's fine to use.
As for macros, there's a few that we can make use of. First up are the standard nochanneling macros for Mind Flay and Mind Sear. I wouldn't recommend using the macro for Mind Flay on this private server. The latency is just too high for US player and even with low latency you'd gain a very small amount of DPS if you would properly time your Mind Flays rather than using the macro. I'd still use the Mind Sear macro though, being lazy can be nice sometimes.
Regular Mind Flay macro. Let's you spam the Mind Flay key without fear of interrupting it.
"#showtooltip Mind Flay
/cast [nochanneling:Mind Flay] Mind Flay"
Same thing as the macro above, just for Mind Sear.
"#showtooltip Mind Sear
/cast [nochanneling:Mind Sear] Mind Sear"
Standard shadowfiend macro. In retail days, the pet has shadowcrawl used automatically, but molten is buggy as **** and it never uses it and it also won't re-us it again. Pressing this macro twice will spawn your fiend and make it use shadowcrawl immediately. I personally recommend using this so you don't have to click the shadowcrawl ability on your shadowfiend which can be quite tedious in high intensity fights.
/cast [pet, nomodifier] Shadowcrawl"
Finally, we have the dispersion cancelling macro. I wouldn’t personally try to combine this with a dispersion macro, since you might activate and de-activate dispersion by mistake. This macro has many uses, some of which are tied to certain encounters, but also just a good macro to have bound and ready to be used.
Q: I don't agree with you on... I think that…
A: Like I said, this is a subjective guide and I don't expect everyone to agree on every single point I make. In some cases, there's no math or theory to back up some of the stuff I claim, and that's things based on personal experience. If you don't agree with me, that's fine, do what you think is best.
Q: What haste rating, crit rating or spell power should I aim for before focusing on one of the other stats?
A: With the current itemization, there's no way to reach the haste cap, nor will you ever be able to get gear that would give you 100% chance to crit all your spells, so just focus on grabbing upgrades to your current gear. Remember to keep a balance between your haste and crit rating. One cannot succeed the other if you want to maintain consistent dps results.
Q: When should I drop Mind Blast and go with the T10 spell priority sequence?
A: Generally, once you've gotten 4-set T10, you can start using the spell priority I outlined above. There's a point where dropping Mind Blast will start yielding DPS benefits. For the lazy people out there, if you have around 5800 gearscore or have started doing heroic 10-man ICC, you're probably good to go with using the T10 spell priority sequence.
Q: Should I really be dropping Mind Blast completely? Is this 100% proven to yield more DPS?
A: You shouldn't really, no. In this guide, I explained it in a simple fashion, but reality is, based on your latency and skill, Mind Blast will still be worthwhile casting, even with 4-set T10 and great gear. There's a few reasons where it shines, for example, it's not channeled, and you can't cancel ticks of it, so you might be able to cast the spell after it faster than for example casting a spell after Mind Flay. You can also use it during other times than just after VT, perhaps to fill gaps where you'd be losing half a second of VT uptime or so.
Q: Why not Black Magic enchant instead of 63 spell power on 1h, isn't it higher theoretical PP?
A: Yes it is, but one thing that will always hold true when it comes to performance is consistency. I personally don't like relying on procs, and if there's ways to avoid it with little to no loss, then I take advantage of them. This particular enchant is one of those things, and I'd rather have my constant 63 spell power rather than relying on a proc.
Q: Why not Icewalker instead of Tuskar's Vitality, isn't it higher DPS?
A: The answer to this question is somewhat similar to the one above. Minor run speed is a great thing to have when it comes to hard modes, and there's many encounters in Icecrown that require you to be mobile, so your speed matters a lot. Anyone serious about doing heroic Icecrown Citadel should be using Tuskar's Vitality, but that's my personal opinion. If you're not doing heroic modes, you can use whatever suits you best.
Q: I got good gear, but I'm still not doing too good DPS, what am I doing wrong?
A: I honestly have no idea. If you stick to the correct spell priority sequence, gear correctly, attain the hit cap then you should be fine to melt faces. If not, you're probably just DOING IT WRONG
Q: Should I be clipping my third Mind Flay tick at some point?
A: Personally, I wouldn't. There might be a tiny theoretical gain in doing so, but I believe that most players are not capable of clipping it precisely enough to gain the DPS advantage especially on this god forsaken server. You might see claims of people doing it, but I discard those as silly tales. Even if you clip it, you might be doing it between the second and third tick rather than just after the second tick. Clipping it before the second tick will outright destroy any kind of DPS gain you got from clipping correctly, several casts would be lost and then some. Really, just don't do it.
Edited: December 4, 2012
This looks very similar to Muqq's shadow priest guide. Not trying to bash or anything, but you could at least point to original author.
therefore you should always go with keeping MB off cd.