Grindfreak has asked me to write up a supplement to his Mutilate information thread, but with an emphasis on Combat builds. I'll start this off by saying that this thread is a generalized source of information; not the end all be all. That would be your handy dandy spreadsheet. Most of my information is pulled from Elitist Jerks and other such sources, and credited to them by default. This sheet is accurate for patch 3.3; and will be updated accordingly whenever I get time and care enough to fix it. And we're off!
Go go gadget Combat!
Combat generally has one spec, with points that will float between Vile Poisons and Improved Poisons, depending on gear and buffs. I've put the weapon skill as swords for simplicity; the Combat tree looks the same for Mace or CQC. The only way to find which split between Vile/Improved is best for your gear is the spreadsheet. Period. Asking for help will result in the same response every time, so just dont' do it.
There are 3 weapon spec choices as of now. CQC for daggers and fists, Sword, and Maces. The weapon specs are all roughly equal, and it will come down to your particular gear to determine which is best. Currently, fist/dagger are the best itemized weapons, so in wishlist gear, CQC will come out ahead.
You will want to use Instant Poison IX on your MH, and Deadly Poison IX on your offhand. Wound Poison is not viable as a main poison anymore; it might have it's place as a debuff but only under those circumstances.
The rotation for Combat has changed sharply as ArP has become more prevalent. It is now fairly easy to reach the point where a Ruptureless build is better dps, not to mention easier and smoother to maintain. Whether your gear can support a Ruptureless rotation, or how much dps you'll be giving up to do so, can only be found through the spreadsheet. That said, it's generally not hard especially if you pick up an ArP proc trinket and have gear with a decent amount of passive ArP on it, such as stuff from the new 5mans.
Your goal is to maintain 100% SnD uptime. A general ratio of dps loss from a dropped SnD is about 6:1; meaning it is better to refresh 6 seconds early than let it expire for 1 second. There is no right or wrong combo point number to refresh with; do it as late as possible without capping energy or dropping it.
Combat has no benefit to starting from stealth. Hit your tank with Tricks Of the Trade, run in, and start your rotation. It's recommended to start off with a 1/2 point SnD, and then fall into your rotation. Starting by Tricksing another DPS is certainly possible, but remember that accidentally killing someone by giving them too much threat is a far greater DPS loss than the difference between the tank and that person for a single Tricks.
Unlike Mutilate, Combat has several cooldowns to work into their rotations; these are Killing Spree, Blade Flurry, and Adrenaline Rush. KS and BF are both on 2 min cooldowns, which reflects nicely with most on use trinkets. AR is on a 3 minute. KS can be glyphed down to 1:15, and becomes harder to stack. Unless you're saving it for a specific burn phase, using it as soon as it becomes available is generally your best bet. The availability of Heroism, and its Horde counterpart Bloodlust, can alter your cooldown usage. It's beneficial to stack your trinket and BF combo (and they should ALWAYS be stacked) during H/BL. If you are unsure when H/BL will be used, pop your cooldowns early in order to have them come up again as often as possible.
KS is much harder to use correctly, due to its mechanics. If the boss has any kind of frontal attack (cleave, breath) or rear attack (dragon tail swipe), you are at risk of being insta-gibbed by either. When in doubt, remember that a dead Rogue puts out the least dps of all. If you can use it safely, you should use it frequently and when you have emptied your energy bar, as you will regain a substantial amount during the attacks and want to minimize energy capping as much as possible.
EP weights are not static, and will vary with gear and raid buffs. A rough list is:
1.92 below 99 (specials cap)
1.68 between 99 and 237/315 (spells cap)
1.28 over 237/315
The 237 vs. 315 is dependent on spell hit reduction raid debuffs on the boss. Poisons use spell hit and spell crit numbers, which is why there are 2 different thresholds to be aware of. Alliance Rogues also can receive the Heroic Presence buff from any Dranaei in their GROUP. This will lower the spells cap to 210.
Expertise is of less use to Combat, with Weapon Expertise lowering the gear requirement and Surprise Attacks removing the dodged finishers. The cap from attacking from behind is still 26/26 on your character screen.
All EP weights are assuming BiS with full raid buffs/debuffs. If you don't get all of these, please, check the spreadsheet.
Glyphs, Gems, and Enchants
Combat gemming is putting heavy emphasis on ArP, in order to close in on either the soft or hard cap. It's generally not a huge increase over Agi or AP, so it's up to the spreadsheet, your wallet, and your desire for min/max to decide which to do with. If you're dual-speccing between Combat and Mutilate, keep in mind that ArP is a poor choice for Mutilate so AP or Agi might be a better choice.
We are also closing in on the crit cap, so be careful of your Agi gems and Agi/Crit yellows. AP and AP/Haste is a very safe alternative.
Metagem is always Relentless Earthseige Diamond. It's value is great enough that there are few helms without meta sockets that are worth it.
Gemming for socket bonus' is not as easy to determine. You will generally want to check the spreadsheet, unless it's a 2nd or 3rd blue socket.
Gem choices are far more spread out now, with AP/Haste/Agi/ArP/Hit/Exp all having varying weights. Please use your spreadsheet, and plug values into WoWHead if you need to see what's available. The only for sure choice is Nightmare Tear for a blue gem to fulfill meta requirements.
Helm: Arcanum of Torment
Shoulders: Greater Inscription of the Axe; Master's Inscription of the Axe (Inscription only)
Chest: Powerful Stats
Cloak: Major Agility; Greater Speed; Swordguard (Tailoring only)
Wrist: Greater Assault; Fur Lining (Leatherworker only)
Belt: Eternal Belt Buckle with red gem
Legs: Icescale Leg Armor
Feet: Icewalker; Cat's Swiftness
Rings: Assault (Enchanting only)
Combat has 2 important glyphs:
Glyph of Sinister Strike
Glyph of Killing Spree
The 3rd slot can have any of these glyphs:
Glyph of Tricks Of the Trade
Glyph of Fan Of Knives
Glyph of Eviscerate
Updated except EP weight, while I look for an updated list of those. Hesitant to use mine, as with really good gear they jump around a LOT.