Of the Rogue's three specs, you've got Subtlety, which is finally living out its fantasy of being a shadowy ninja, and you've got Outlaw, the new name for Combat that is really committing to being a Pirate. So where does that leave Assassination?
Honestly, it's leaving them with most of the old class features that used to define Rogues.
Assassination Rogues are now the only spec that has access to poison. It works just like it does on live, giving you an hour-long buff that adds effects to your weapon strikes. You can still have one lethal poison and one non-lethal one at any given time.
You'll also get a new ranged attack to replace Throw (all three specs get their own ranged attack) which is Poisoned Knife, costing 40 Energy and guaranteeing an application of your two poisons, but not doing enough damage to really justify it in the main rotation.
Bleeding All Over the Place:
Assassination also becomes the only Rogue spec with Bleed effects, making them masters of the DoT (Sub does have Nightblade, but that does Shadow damage, so it doesn't count as a bleed or poison.)
Rupture remains the finisher you'll want to maintain at all times on your target, and it continues to have the Venomous Wounds effect to help with your Energy regeneration.
The new twist is that Garrote now becomes a constant part of your rotation. The ability no longer requires Stealth, but you'll only get the silence effect if you use it from Stealth. Thus, you'll want to make sure that this is constantly ticking on your target throughout the entire fight. The ability also now has a 15-second cooldown and lasts 18 seconds, so you'll only be able to keep this on one target, realistically.
And of course, any bleed on a poisoned target will trigger Venomous Wounds, so in a two-target situation you can start off by Garroting one and Rupturing another.
Much as I loved it, Dispatch is gone. Not only are they really consolidating "Execute" style attacks in Warriors, but they're also making Assassination a much more predictable and steady rotation - if you like this proc, you might want to check out Outlaw, which has a similar kind of rotational proc in it's Saber Slash/Pistol Shot combo.
Death of a Thousand Cuts:
Assassination is definitely more focused now on damage-over-time effects. You'll still use Envenom and Mutilate, and a lot of your old tools are still there. In fact, other than Dispatch and Ambush (and you'll be using Garotte anyway,) I think everything's still there. Vendetta is still your big cooldown.
There are certainly new talents, though. Still, Assassination is the Rogue spec for players who don't want change.