For Combat.
Fight dependent Combat can be the best spec there is for rogues. In current content (4.2) it is a fair amount better than any spec on Lord Ryolith and Majordomo Staghelm due to cleave. In addition to the cleave it also adds 4% physical dmg increase from Savage Combat (frost dk/ravager hunter pet/arms warrior also provide this). Combat is very competitive on all fights, it just excels at those two in particular.
Another advantage Combat has is that it prioritizes expertise more than Assassination, so those fights where you're highly frontal; like Rag and to some extent Domo it suffers less.
Stat priorities for Combat start the same as every other rogue spec, agility is king. Afterwards it goes yellow hit (5%) for specials (and you get 6% from precision) then expertise (26/26) and haste once capped. Haste is significantly better than any other stat at this point so drop all you can, your worst stat being white hit (post 17%) and crit.
The most common spec would be 7/31/3
There are quite a few "filler points" for combat so it is up to you if you want imp sprint/imp kick etc. This is the spec I typically do and I find to be the best overall.
Glyphs: Primes glyphs being Sinister Strike/Adrenaline rush, and usually Slice and Dice.
For Majors I would recommend Blade Flurry/Feint/Tricks.
Minors are up to you, I enjoy blazing speed, but I don't use it in all my specs, more of an occasional fun factor than useful from a PvE raiding perspective. Typically I have safe fall, blazing, and poison/lockpick. I would recommend poison if you're not crazy like me and reapply poisons at 30 min mark so you never run into a mid fight issue of no poisons.
Rotation for Combat can be semi-difficult to fairly easy. Here is what you need to know:
SnD: First and foremost is Slice and Dice, keep it up as close to 100% of the time as you possibly can, sacrificing other things to do so if you must.
Insights: Insights will increases your damage done by 10/20/30% depending on your level of insight. You gain insight by using SS (Sinister Strike) or RvS (Revealing Strike), after you use 4 of these consecutively on the same target you gain shallow insight, which is 10% damage increase for 15 seconds, the duration is refreshed to 15 seconds each SS/RvS you do within 4; at that point your insight will change to 20% (moderate insight) and will follow the same structure. When you get 12 abilities in and gain "deep insight" you'll be doing 30% more damage for 15 seconds, however as you SS/RvS your duration will not reset to 15 seconds like it had previously and the amount of SS/RvS you do will not contribute to ending the insight series, nor will it help you gain shallow insight again once finished with your deep duration. In the other insights your % of damage bonus will be longer, but less %, once those 15 seconds are up during your deep insight you'll be reset to 0% again. Once the deep insight is over any SS/RvS will contribute to you going back into shallow insight, but none during the duration of deep insight will effect it, for instance if you have deep insight and do 12 sinister strikes in 15 seconds you'll still be deep and once deep ends you will be at 0 and need 4 more SS/RvS to gain shallow.
One thing to mention is that if you change targets you lose your insight and of course cp (combo points), however if you redirect you do not, so if you need to swap targets less than once per minute it isn't as huge a loss as it would be otherwise. When you switch targets even with redirect though it will not move your poison stack or rupture.
Rupture: This one is kind of up in the air, personally I don't usually roll rupture while I'm combat. I think keeping rupture in my rotation overcomplicates it and is not much of a gain. On a stand still fight (or mostly a stand still) like Baleroc, sure I'd say use Rupture, otherwise it is up to the player to decide if they feel it is easy to maintain in the rotation or not. I would say try it out, if it is difficult or choppy for you, drop it for a while and see how you fare, I've ranked on Stag 10/25 and Ryo 10/25 as combat without using Rupture, iirc it is ~1% dmg loss? Which would be 20-30dps typically.
RvS: Revealing Strike increases the damage of your next finisher by 35%, it is not worth doing unless you are at 4 cp. So if you have SnD up, you SS to 4, RvS, Evi (Eviscerate). If you have SnD up, you SS to 3 then Glyph trigger to 5, Evi, do not RvS. It is fairly simple.
While you're doing your rotation I find that this spec is the easiest to tunnel vision. Tunnel vision if you don't know is ignoring everything but your damage and rotation, often ending up in you dying by missing a mechanic/standing in things. It isn't the most difficult rotation, but I think it takes the most "mashing". You're energy cap is 100 and has the highest rate of return than any other rogue spec, making it easy to cap out if you're not constantly bashing SS/RvS/or Evi, etc. I would suggest trying to make your ability usage fluid and watch your surroundings, don't worry about mashing until you're really good at not dying on certain fights. That could be said for all specs, and a strong tip overall, but it might be my massive Assassination experience talking here making Combat and Sub feel clunkier to me personally.
Rotational tip: If you wait to use KS (Killing Spree) until you have shallow insight it will always refresh on deep/shallow so you get more out of it; instead of using it immediately and then waiting until your 2nd deep to use it. If you wait until your first shallow it'll be refreshed by that 2nd deep still and you get an extra 10% out of it consistently.
Gems: Always use Delicate Inferno Ruby unless you're matching a socket for an agi bonus, in that case use Glinting Demonseye or Deft Ember Topaz. Agi is, as for all rogue specs, your best stat by a large margin.
So for combat you want to open as near to the target as possible (stealth if you can) but you don't get anything out of opening from stealth itself, I just SS. Once you SS (or SS a couple times) get your SnD up and keep pushing SS to 4/5, when hitting 4 use RvS then Evi. If you choose to incorporate Rupture in your rotation it takes priority over an Evi.
Poisons: Poisons are the same as Assassination, except ranged, you wand IP (Instant Poison) MH (Main Hand) and DP (Deadly Poison) OH (Off hand) with WP (Wound Poison) on your ranged for fan.
BiS list links take a while so I'm going to save those until a later post, but they will be coming sooner rather than later.
Hope this post provided some insights into Combat for some, or at least helped on some basics for less experienced rogues. Feel free to post or in game mail me on Lightbringer if you have any questions or comments.
-Ochiru
edit: grammar, and forgot poison.
