First and foremost I would like to say that NONE of this is copy and pasted from EJ. This comes from MY experience as a rogue and the questions I have seen in the forums and in game. This guide will take you as far as normal raiding content, for everything after that (Heroic Raid Bosses) I would go to the Elitist Jerks thread.
Mut Rogue specs:
So let's get started. The first question I see is, "What is a good spec?"
2/3 Precision(Considered the most "optimal spec")
Deadend Nerves over Deadly Brew
My spec - In my spec I have 3/3 in precision to ease my need for hit so that I can reforge/gem into other high priority stats.
There are other variations but I have found that those listed have the highest dps output. The Deadened Nerves and Deadly Brew talents are fillers and that point may be put anywhere without losing dps.
"But I PvP, what about me?"
PvP spec 1
PvP spec 2
Glyphs:
There is no longer a debate about glyphs, these ones listed provide the highest dps:
Prime - Mutilate, Rupture, Backstab
Major - Feint, Sap, Tricks of the Trade
Minor - Safe Fall, Blurred Speed, Poisons
For major glyphs I would have to say that Feint is a must. Feint is an amazing ability not just for reducing threat but for reducing AoE damage done by bosses and mobs. Sap is invaluable for CC, especially if you're the only CC in the group.
Minor glyphs don't matter, not a single one of them is a dps increase unless your poisons fall off in the middle of a fight. The lockpicking glyph does work nice in a few spots (Heroic Deadmines while in the nightmare, after killing the Harvester you can lockpick the door and move to the next spot before it begins)
Rotation and Cooldowns:
Your number one priority when starting a fight is to start it in stealth and open with Garrote. There are two reasons for this;
1. Overkill, when you first come out of stealth and for 20 seconds after that you have increased energy regeneration. You want this buff so that you can put up Rupture and SnD ASAP.
2. Garrote, when combined with overkill this gives you HUGE energy regeneration at the beginning of the fight. Right before a bloodlust/heroism/time warp I will use Vanish and reapply Garrote to maximize energy return during that burn.
Other then that the rotation is fairly simple for single target:
4+ CP SnD, 4+ CP Rupture, 4+ CP Envenom
Mutilate is your source of Combo Points (CP) until the boss reaches 35%.
After applying Rupture and Getting SnD going it just comes down to keeping your Envenom buff up and refreshing Rupture whenever it falls off. SnD will always be refreshed whenever you Envenom and you "shouldn't" have to reapply it. As for the Envenom buff, try to avoid clipping it (clipping = refreshing before it falls off), but it's better to clip it than let your energy reach max and stay there. It is not a dot and refreshing it before it wears off is not a significant dps decrease but you should hold out until it does fall off to maximize its uptime.
WARNING!!!!! WARNING!!!! THE BOSS IS UNDER 35%!!!!!!!!
At this point you switch from using Mutilate to using Backstab. Also, it's not 4+ CP anymore, you Backstab till you have 5 CP then use finishers.
AoE rotation is handled in one of two ways:
1. Spam Fan of Knives (FoK)
2. Apply rupture to several targets then spam FoK
The rotation used depends on how many mobs there are and how long they will survive. If you know they will die quickly then TotT to the tank and spam FoK and enjoy your 20k AoE dps. If your using the 2nd form of the AoE rotation put up ruptures on three or four mobs only using one Mutilate per mob for CPs.
Cooldowns:
Assassination rogues have three cooldowns (outside of trinkets like Unsolvable Riddle and profession based abilities like Synapse Springs). They are Vendetta, Cold Blood and Vanish.
Vendetta: You will want to use this ability whenever it is off cooldown and when you can stay on the targetted mob/boss for it's duration. It is not advised to try and use this during AoE since it only effects one target. When used it will place a debuff on the target that will last for 30 seconds (36 if glyphed).
Cold Blood: This ability generates 25 energy and makes your next non-periodic damage ability have a 100% crit chance. EJ says to use this when you are about to use a 5 CP Envenom. So if you are going to use it like that make sure the 25 energy gained will not cap you. DO NOT use while spamming FoK since it's non-periodic damage is low.
Vanish: This ability is amazing for DPS gains. When used you will regain Overkill and be able to reapply Garrote. This is best used before your group uses bloodlust/heroism/time warp unless that ability is used at the beginning of the fight when you will have Overkill and Garrote up anyway. If your group is using bloodlust early I would suggest using this before you reapply Vendetta the second time.
Poisons.
For PvE you want Instant Poison on your main hand, Deadly Poison on your off hand and thrown weapons.
For PvP you want Wound Poison on your main hand, Deadly Poison on your off hand and thrown weapons.
You should have spec'd into deadly brew so there is no need for Crippling Poison. Wound Poison is used in PvP for the healing reduction.
Weapons.
1.8 Main hand and 1.4 Off hand. Both slots will be daggers since most of our abilities require a dagger to use.
Stats/Gems/Reforging:
Stat Priority: Agility > Spell Hit Cap (AkA Poison hit cap) > Mastery > Haste > Crit > Expertise
Raw Agility is your best stat, there is nothing better.
Spell Hit Cap or Poison Hit Cap is just as important as Agility. 17% is the Hit Cap, but you have to look under "Spell" in your character pane to see it. This is not the Melee Hit Chance.
Haste and Mastery, what to say here? These stats are equally as important and you want them both as high as possible. The more Haste you have the more melee hits you will perform which means faster poison application, and faster energy regeneration. Mastery increases your poison damage. Poisons are the main source of a Mut Rogues dps.
Critical Strike........ it's the stat we reforge into other higher priority stats. It's not completely useless since ability crits add an extra combo point. But dont reforge or gem into it.
Expertise, this is our lowest stat and all the expertise you need will come from gear. You do not have to reforge, gem, or enchant into this stat. When a rogue is dodged/parried/misses we are refunded 80% of the ability cost (i.e. you only lose 7 energy when an Envenom is dodged/parried/misses).
Gems:
Delicate Inferno Ruby (red) - 40 AGI
Adept Ember Topaz (orange) - 20 AGI 20 Mastery
Glinting Demonseye (purple) - 20 AGI 20 Hit
These are the gems I use (minus my cogwheel sockets) in all of my gear. I go for all socket bonuses which are normally either 10/20 AGI or 10/20 Haste. Many people will say that if the socket bonus isn't 20 AGI then don't go for the bonus but what's the fun in that? Your gonna have all red gems in your gear except maybe one or two pieces and variety is the spice of life (and what rogue doesn't like a little spice huh?). The only socket bonuses I would ignore are Crit and if it exists Expertise.
Reforging:
After you reach Spell Hit Cap you want to reforge into mastery wherever possible.
When looking to reforge gear I have always followed this;
Expertise > Mastery/Haste (if the item has haste reforge to mastery and vise versa. If it does not have haste or mastery, reforge into mastery)
Crit > Mastery/Haste (if the item has haste reforge to mastery and vise versa. If it does not have haste or mastery, reforge into mastery)
Expertise > Hit (if under spell hit cap)
Crit > Hit (if under spell hit cap)
Unfortunately you can not reforge into Agility or else that's all I would have said here lol.
Tips and Tricks
A section that the community can help me with. Tips and tricks for bosses and what abilities help/hurt you on them.
Heroic Valiona and Theralion
Sub rogue guide for this fight, use it and love it.
Cho'gall
-Blind interrupts worshiping, for those healers/casters too far away to kick.
Al'akir
-Goblins, do not use rocket jump in phase 3, you will just fall to your death and be laughed at. In phase 1 it's amazing for jumping back into the boss after a wind burst.
Magmaw
-If you get chosen to jump up and chain him you don't have to stay up the whole time. Hit the chain and make sure he is snagged, then press the exit vehicle button to get down and help quicker.
Nefarian
-Feint reduces the electrocute damage, time your feints with electrocute casts.
Resources:
The in-depth Elitist Jerks Mut Rogue guide - Includes all the math and heroic raid content information.
ShadowCraft - Amazing website for reforging/enchant/gemming for any rogue