Should I go for my tier 11 four-piece bonus?
The short answer is yes, Deadly Scheme is worth wearing four pieces of our tier 11 set. The long answer is still yes, but with a caveat: Unless your guild is regularly killing Nefarian or Cho'gall, you're not going to be able to score four pieces of the set. You can buy the gloves, pants, and chest from the vendors for valor points (or get lucky against Argaloth), but the shoulders and helm of our set require tokens from the two end bosses of Bastion of Twilight and Blackwing Descent. Our two-piece bonus is also very strong, and you'll probably want to aim for that first, but you can't even get your four-piece without killing a difficult boss.
If you're in a guild that's killing Nefarian and Cho'gall on a regular basis, you can usually pick up your four-piece without too much trouble. In terms of using the new bonus, you should simply play your rotation as usual. Assassination rogues will easily be able to use one Envenom every 15 seconds, making sure they never waste the proc. If you're playing combat, just make sure that you unload your Eviscerate before the Deadly Scheme buff expires. Subtlety shouldn't have any issues with squeezing an Eviscerate in, as sub's combo point generation is quite rapid.
Tips for Blade Flurry usage
My biggest piece of advice for a combat rogue trying to maximize Blade Flurry is to drop Rupture from your rotation while BF is active. Since Rupture isn't replicated through BF, you're only applying the debuff to one target. You could Eviscerate instead, which is then replicated on both targets, dealing double damage. The rotation essentially collapses into an Eviscerate/Slice and Dice spam until there's no longer an additional nearby target for you to cleave.
When is subtlety viable?
There's a lot of talk about subtlety in the various rogue circles, and I know several rogues who would love for the spec to be more competitive in PvE. Right now, subtlety is behind both combat and assassination in terms of DPS, and it's also more complicated to play. The spec suffers huge penalties whenever you can't focus on a target for long periods of time, and it has the worst AoE damage of any rogue talent tree. Subtlety simple doesn't excel at anything, in terms of DPS, and that's why you won't see any rogues posting amazing World of Logs parses of their subtlety DPS.
The one thing sub does have going for it is survivability. It's almost impossible to kill a subtlety rogue, especially for a raid boss that doesn't know any better. Subtlety has seen some usage by high-end rogues on fights with heavy incoming damage, especially the Valiona and Theralion heroic encounter. Unless you're playing a rogue at the highest level, there's really no reason to keep subtlety around as a PvE build. Now, if you want to PvP, subtlety is more than potent. Just make sure that you spec back into combat or assassination if you want to be taken seriously in your raid.
What poisons should I use for Mutilate PvP?
While subtlety is my preferred PvP spec due to the abundance of utility and survivability talents, assassination builds are still pretty strong. After consulting with some of my rogue colleagues, the best poison mix for Mutilate in PvP is Instant/Deadly. You need to have access to Envenom to finish off a target that's being healed, which means Deadly Poison is required. The question is usually whether Wound Poison or Instant Poison is more effective on your main dagger. I find that the mix of the Improved Poisons mastery bonus, the Envenom buff, and Potent Poisons push Instant Poison's damage way ahead of Wound's. Since we're a DPS class, we're looking to maximize our DPS, and Instant/Deadly is the best way I've found to accomplish that.
Various questions about assassination's rotation
Let me start by saying that there's nothing wrong with using 4-point finishers as an assassination rogue. I've heard of rogues using Shiv or Sinister Strike to up their combo points to the perfect 5, but it's a significant DPS loss. As an assassination rogue, you only have to CP generators: Mutilate and Backstab. If you're stuck at 4 combo points, just use the finisher anyway. The reason is that combo points are worth a ton of damage, and wasting them is awful.
There's a great chart of "damage costs" on Elitist Jerks that goes over how much damage you lose when you make a mistake with your rotation. Generating too many combo points is right at the top of things not to do, and so you'll always want to keep that in mind. When you're trying to figure out what to do, it's almost always better to either Envenom early or to use a low combo point Rupture. Wasting a Mutilate or Backstab is incredibly costly, abuse your finishers instead.
Check back every Wednesday for the latest rogue strategies, from rogue basics and kicking your interrupts into high gear to how to handle your dual-spec rogue and how to pickpocket top tips from top-performing rogues.