It appears that there may be somewhat significant class and balance changes in 5.2, so lets keep discussion of them to this thread for the moment.

As usual, please try to keep it constructive. Its fine to not like some of the changes, but try not to be whiny about it.

Blade Flurry now does 25% damage to the second target, instead of full.

Note: Datamined changes removed in favor of official Blizzard announcement where they overlap
Datamined 12/21/12

• Hit and Run (New) - Immediately teleport to a targeted location, leaving a shadow of yourself behind. Upon activating the effect a second time, or after 10 sec, you will return to your shadow's location.

Posted 12/21/12

• Preparation is now a baseline ability learned at level 68.
• Versatility has been removed.
• New Level 90 Talent: Marked for Death - Marks a target and instantly generates 5 combo points. When that target dies, Marked for Death's cooldown is reset. This talent has a 1 minute cooldown.
• New Level 60 Talent: Cloak and Dagger - Ambush, Garrote, and Cheap Shot now have a 30 yard range, and will cause the Rogue to teleport behind the target.
• Burst of Speed now costs 30 Energy (was 50 Energy), can be used in Stealth, and always grants increased movement speed in addition to breaking snare effects, but no longer breaks root effects.
• Shuriken Toss now causes the Rogue to throw shuriken instead of autoattacking for 10 seconds after Shuriken Toss is used.
• Deadly Throw can now interrupt spellcasting when used at 3, 4, and 5 combo points, and upon interrupt prevents any spell in that school from being cast for 4, 5 and 6 seconds respectively (was 5 combo points and 6 seconds).
• Nerve Strike now reduces the effectiveness of healing provided by the target by 25%.
• Shadow Focus now reduces ability energy costs by 75% while stealthed (was 100%).
• PvP set bonuses have been changed:
  Vigor is now the 4 piece set bonus and increases maximum energy by 50 (was 10).
  Deadly Brew is now the 2 piece set bonus, and its effects remain unchanged.
• Vitality now increases attack power by 30% (was 25%).
• Blade Flurry now deals 75% less damage. (Datamined wording: "Blade Flurry now does 25% damage to the second target, instead of full.")
• Sanguinary Vein now increases the damage the target takes by 20% (was 16%).

So, initial impressions:

1) Blade Flurry is basically useless if that information is correct. It wouldn't surprise me if this is a bad data-mine, but if it is correct I expect them to back off on this nerf before it goes live - not that they might not reduce the efficacy of Blade Flurry, but I doubt they'd nerf it quite that much.

That said, while a Blade Flurry nerf would resolve the imbalance in cleave efficacy across specs, it would also mean rogues have no useful cleave at all, which is... potentially concerning, as they're generally important on a number of different fights.

2) Shuriken Toss is now somewhat more appealing, as you'll do a much larger portion of your single-target damage with it. That said: it still has the problem that you don't really have a finisher (you can use Deadly Throw, but compared to Envenom/Rupture/Eviscerate, and without Bandit's Guile, its still a significant DPS loss). So when you're stuck at range, you'll do a larger portion of your regular damage... but still a lot less than a proper ranged class. So in practice, I suspect this rarely winds up being the optimal choice in raids.

3) Marked for Death should give us some nice burst for target switching. On a single-target burn its not going to make too much difference, but for, say, Garalon legs, the ability to open each leg with a full 5pt finisher will result in a respectable DPS increase. That said: I suspect rogues still ramp up more slowly than many other classes; the impression I get looking at Recount in the opening seconds of boss fights is that almost every class opens faster than rogues, and by more than 1 finisher will fix.

That said: that may also be a cooldown issue, so we'll see how it plays out in practice.

4) Hit and Run is interesting, although I'm not entirely sure how good it winds up being. Its certainly a creative and interesting ability, but I'm not sure how often we're going to want to swap off our current target for less than 10 seconds at a time. I'm sure it'll happen, but it strikes me as a bit... niche.

Might shed some light:

Patch 5.2 PTR Patch Note Preview - World of Warcraft

My views in order:

1) Change to prep is nice, should allow most flexibility in pvp but pve will see some small but nice gains
2) Versatility removed doesn't address difficult and awkward target switching; without making it a clone, isn't the chi system where CP "sticks" to you a better solution
3) Marked for death seems usefull in pve and a good competitor to anticipation. I would imagine it would a DPS gain to take this one over anticipation, but would require more skill to manage CP generation. Can see it being extremely OP in some fights like elegon p2 where you would have a crazy amount of CP to use.
4) Cloak and dagger seems pointless when SS is the other choice to take. There is no way you can stealth frequently enough to beat SS.
5) BOS granted a much needed change, 30 energy is much reduced but doesn't provide immunity. PVP can still be considered a strong option and might find it's way in to PVE in movement heavy fights where SS just isn't enough
6) Shruiken Toss neat for PVP, again useless for PVE (unless these shruikens are more powerful than meleeing) so in my eyes another failure to balance the tiers for both PVE/PVP
7) Nice change to Deadly throw for those who use it as in PVP you're never swimming in CP
8) Nice buff to nerve strike
9) A possibly unnecessary nerf to Shadow focus, maybe to bring it in line with the other talents but blizz clearly missing the point that there will always be a winner in that tier so poor design IMO
10) A humongous change to PVP tier set, will now provide potential for larger burst
11) Slight buff to combat damage
12) Pfft, nothing to say here. An unmitigated disaster for combat rogues, It's probably more beneficial to single target than to attempt a cleave now. A completely unnecessary change here... Words can't express.
13) Buff to subltelty to bring in line with assass PVE damage I suspect

Please let me know your thoughts, bare in mind these are my views...

Counter argument to the Shadow Focus nerf would be that Prep is now a baseline talent so offers more usage of the Shadow Focus talent. Although personally I feel it's completely unnecessary when Shadow Focus is fine as it is.

Kinda curious to see if Versatility will end up being baked into Redirect (highly doubtful, but one can remain hopefully), Marked For Death offers a decent substitute though with the cd resetting when the current target dies and offering an instant 5 CP on the current target. Could offer nice Burst on fights where adds are fairly prominent although I'm not entirely sure how long Marked For Death debuff on the target would last.

Most are good changes, the one i cant understand like most of you is the BF nerf, I know its too strong but in those notes they will need to either remove the energy penalty so BF ends up just as some extra damage or just up the damage to atleast 50%

I'd like to point out that I was strongly considering taking even the 5.1 verison of Shuriken Toss for H-Emperor's Will, since I solo-soak all Titan Sparks (10m) and I therefore have lots of time away from target, making the DPS loss consequent. The 5.2 change will make this option all the more compelling.

I think "Marked for Death" in the current iteration is a very strong PvE option (probably too stong), and I will highly enjoy testing the hell out of it.

To my main point: I'm sorry if this opinion is not shared by the majority of the Rogue community, but I *love* the Blade Flurry nerf. I have felt forced into Combat Spec for too long for too many fights. I strongly prefer playing my spec of choice (Asassination), but I will grudgingly play any other spec when the difference is as high as it is currently for Cleave fights. By nerfing the difference to less than 10%, I can keep playing my spec of choice (which I play much better than I play Combat btw) without remorse.

Now I strongly hope that Blizzard follows Aldriana's option 3™, gives some alternative cleave to Assassination and Subtlety and subsequently buffs BF back to something like a 30% DPS gain, but meanwhile, I'll take what I can and enjoy finally playing my spec of choice on most fights. I'm sincerely sad that it has to come with this kind of price to pay for Combat rogues, but the current situation was very much lessening my enjoyment of the game.

You could also change combat with assa and cleave with AoE and you are on the same boat, combat/sub rogues are "forced" to play assassination for AoE purposes, both speccs have a niche in pve that doesnt mean one or the other are supposed to be nerfed to the ground

I imagine if they got rid of the energy regen penalty along with that 75% nerf, that it would be ok. Damage would be a little more consistent and the playstyle would be more twitchy which is likely what they prefer. I find BF really slows down my rotation and gets rather boring quickly over long periods of cleave. The cons with no energy pentalty is that it would no longer be a toggle, and Combat Rogues would have it up at all times. That may not really be so bad, however. It would finally make combat the absolute cleave spec and really give it an identity. I kind of like that, although somehow I doubt it will ever get there.

Without a change to the energy regen it's a pretty nasty hit to what we are accustomed to as combat rogues. Even if it is still worth it (as Aldriana said), that's assuming 100% perfect uptime on 2 targets. One target goes out of range for a few seconds and now BF is almost not worth it whatsoever, or a DPS loss if it's not toggled fast enough. I see this as too thin a line.

Part of this is a 5% AP buff, but in that contrast it would make a whole lot more sense if the intent was BF did 75% of the damage instead of 25%. (not saying that would even it out)
A bit more maintarget damage, and less offtarget damage.

Seems unlikely that 5.2 will ship with this huge BF nerf if there isnt something else there to counter it, which there does not seem to be in the patchnotes atm.

Just and idea but pairing Marked for Death with BF may be a possible reason for the nerf.

I'm pretty excited by these changes. They are, perhaps employing to heavy a hand in regards to BF, but the rest gives me hope for a solid opening rotation single target. I've always enjoyed combat over the other specs, I don't see that changing.