Much as I've been doing for tanks, I took my Rogue who has gloriously returned to Subtlety - the spec that made him my first character to hit level 70 when that was the cap - through a few Timewalker Dungeons, appropriately enough, the Burning Crusade timewalker dungeons.
While I had some frustrating Shattered Halls runs and not one but two experiences - today - of jumping into Black Morass with a shield down to less than 50% and four portals open and no apparent way to reset the instance after Medivh was killed, I did manage to finish 5 dungeons and get the quest done, inevitably getting a piece of gear that wasn't as good as what I already had, despite the fact that this character hasn't even run Hellfire Citadel in any capacity.
There's one big note that I discovered after writing my little Subtlety primer earlier in the month, which is that Shuriken Storm - our new Subtlety version of Fan of Knives (Assassination keeps the old ability but I think it has a new graphic and specifically talks about poison) - actually does three times its normal damage when you're stealthed or in Shadow Dance.
Especially since I've been playing Assassination for the last three expansions or so, I've been used to thinking of Fan of Knives as something only to be used in really large groups, and just Mutilate-Multidotting any time you've got fewer than like six enemies.
Subtlety uses Shuriken Storm like Elemental uses Chain Lightning. Any time you've got an additional target, you use this.
Now, the damage is not actually very competitive with Backstab (I use Gloomblade because I want to be able to solo and quest without any penalties, though that's arguably less of a big deal due to what I'm about to get at,) but Backstab is a relatively small portion of your damage. It's really about building up combo points, and Shuriken Storm, which gives you a CP for every single target hit, will be far more effective at doing that.
So my strategy has been to Shuriken Storm and then put Nightblade on every target in a trash pack. If the pack manages to still be alive by the time that I've put Nightblade up on everyone and it isn't about to fall off the first guy I hit, I'll start working in some Eviscerates, but generally the trash packs were dying before that became an issue.
Nightblade is... Here's the thing about Nightblade. Assassination got all of the Bleeds and Poisons that Rogues had previously had, becoming the real DoT-spec for the class. But in place of Rupture, Subtlety has gotten Nightblade, which for all intents and purposes is basically just the same thing. Sure, it's got a shorter duration, does Shadow damage instead of physical (though Rupture's a bleed, which ignores armor as well) and there's the slowing component, but ultimately it's just a DoT that you need to maintain while you try to generate CPs faster to get off more Eviscerates.
Clearly Sub needs more than one finishing move, and I don't want them to touch Shadow Dance, as I like it fine the way it is now as a semi-cooldown/semi-rotational ability. I just wonder if Nightblade is the most interesting or even flavorful thing to use. I mean, I don't even really know what it means to "Nightblade" someone. It uses the same animation as Rupture, so it's like we're tearing into them, only in a more spiritual sense?
If anything, Nightblade seems like it would be more of a self-buff akin to Slice and Dice - you could imagine that it turns all your attacks into Shadow damage, which would of course be a buff to their damage in most situations.
Granted, that also steps on the toes of Sub's big damage cooldown, Shadow Blades (which is mostly fine as it is) and also would leave their AoE rotation needing something more. I'd love to see a return of some kind of Crimson Tempest-style ability - just a straight-up AoE finisher. You'd re-tool it to feel more Subtlety-like, but you'd need something for the AoE.
Talent-wise I'm breaking with Icy-Veins' recommendations (which is always an option, especially if you're not doing serious raiding) because I think that build is more specifically for long-term raid boss fights - something I don't expect I'll do a lot of until a month or so into Legion (whenever the first LFR wing comes out.) Tier 1 I went with Gloomblade, mainly for soloing (though given that Backstab's portion of your damage is pretty low and that you can now still use it when the target is facing you, just at a damage penalty, this might not be so important anymore.)
Tier 2 I went with Shadow Focus. I tried Subterfuge, but even though my Shadow Dances were lasting longer, I didn't have the energy to get off all the Shadowstrikes I could fit in that window, and so I just did more damage in a shorter period of time with Shadow Focus (which, you know, means more damage per second) so I went back to that. I imagine that if you have really good gear (my guy is somewhere in the mid 690s) with lots of haste this might work better for you, but I just really like Shadow Focus.
Tier 3 I use Anticipation, largely so that I can spam Shadowstrike within Shadow Dance (with the Premeditation talent later on) and not waste too many CPs. I suppose if I didn't have Premeditation I might go for Vigor, but the other options are Enveloping Shadows (which I'd be fine with if it replaced Nightblade, but I don't want to go back to the "balance finishers" design for Subtlety) and Alacrity, which is such a slow build that in anything other than a raid boss, you're going to build it up only for it to fall off once you've gotten it.
Master of Shadows I love (level 100 tier) because it gives you Energy right when you need it.
For the "survival tier" at level 60 I went with Soothing Darkness, because much like Second Wind for Arms, this a really potent out-in-the-world heal. When you're moving from enemy to enemy while soloing, you're generally doing it while stealthed. Thus the damage you take during each fight will get healed back easily and allow you to save your Crimson Vial for emergencies.
One talent that can get you into trouble is Strike from the Shadows (75 tier,) which makes your Shadowstrikes stun the target for two seconds. This is incredible when soloing and also can be very useful in groups, but it also can make you seriously anger your tank if you screw up their pulls (like if your Paladin tank silences a caster enemy with Avenger's Shield to force them to run to him only for you to stun the guy and allow the silence effect to fall off,) so if you go with this talent, make sure that you target enemies that are already near the tank or at least go after melee adds (and toss in a nice Tricks of the Trade to help your tank out while you're at it.) Still, this talent can also really do wonders for the survivability of you and your group.
Between Shadowstrike and Shadowstep, you'll be able to zip around the battlefield with ease. I really love the way it feels - giving you a real Nightcrawler sort of superpower. It also means you can be kind of lazy about positioning because if you ever get out of position, your next Shadowstrike will put you in the right place. Just be careful around any enemy that has a tail-swipe. You might not want to use this bonus in a case like that.