First thing is that people are labeling all rogues by the "rogue" archetype. If you want to look at a rogue in WoW look no further than your friendly neighborhood Defias roaming the hills in Westfall. That's a rogue. An outlaw. Nothing more too it than a person living on the fringe of society getting by on whatever means he can which usually resolves to robbery or other forms of crime to survive.
But, that's just the archetype is an outlaw. A person who believes themselves above the law and who can do what they want when they want and that the rules don't apply to them. But the rogue is not just a rogue. We have specializations upon which we embark to make our character more than just the plain basic rogue. That's why while each class shares some of the common dirty tricks and stealthy aspects I personally believe that they are in actually different classes (although they have similar play styles but that's a different topic). Instead of the honorable knight who puts forth his family honor before everything you have a scoundrel who will insult your mother, call your wife a whore and say you're just like your worthless father, trick you into a duel and then use every sort of dirty trick in the book to kill you and then take your coin purse when he's finished. You have a master poisoner who relies on his poisons to do his dirty work inflicting far more harm with a cut than anything else. And then you have the one who sneaks about and kills his target with a single swift blow to the back and then vanishes into the crowd before anyone knows what happened.
Now I think they got the names backwards here. Subtly should be about the subtle way's of poison. Slipping a drop of deadly poison in their targets drink while no one is watching and then being miles away while their target suddenly drops dead for no apparent reason. Mean while assassination should be about just that. Ambushing and backstabing someone to death. Assassinating them. While obviously it's possible to assassinate someone with poison typically when someone hears of an assassination attempt it's more often than not someone with a gun trying to take a person out. Now obviously you can't have a game where on Tuesday you sneak through the current raid and poison everyone's food supply and then come back on Monday and collect all the loot just lying around there on dead guys and you have to have some sort of game play element tot it. I think both classes have their niche from an RP aspect they just goofed the names up.
Now about combat it should be that. Focused on combat. Think of a duelist class who doesn't revolve around stealth but weapon skill and agility to dodge and parry. They should have stealth because they are a rogue so for a person like that to be sneaking around definitely fits but they shouldn't get any stealth abilities aside from stealth it self. Even as it stands now combat has almost no reliance on stealth as it is and if it had an alternate form of garrote/cs/sap that weren't used in stealth they'd have the same game play now as they always have. Right now combat is somewhere between a pseudo stealther and a berserker smashing buttons and attacking as fast as possible with no elegance or flair. Combat has all the nuances of a little boy closing his eyes and windmill swinging his arms and charging at someone blindly.
I think the biggest detriment to the rogue class that has completely destroyed everything rogue about it. The thing that has changed the rogue from the stereo typical "rogue" in most RPGs and has turned it into a boring passive damaging snoozefest has been rated arenas and trying to get them into E-Sports. In every game out there the backstab rogue is the guy who can run around trash literally one shotting stuff with crit after huge crit after huge crit and then when they fight a boss their pretty lame because they rely so much on that burst and stealth attacks. That's the way rogues used to be and that was their thing. Aside from combat they were a burst class. They speced down into talents that made BS and ambush crit almost every time. They had low passive damage and low over all damage but they could chain some abilities together and do massive burst. But now everyone has giant health pools, rogues have been nerfed to the ground so that all our damage is passive and boring and our burst which used to be the best in the game now is the worst. FPS games are a great example of how PvP can work really well. You have all sorts of specs some which are more up front in your face and some which are long ranged. You use your surrounds to your benefit and each map has a huge game play difference compared to modern day arena which is what 5? different ways that you can see people running around pillar humping. The backstabbing crit based rogue should be the sniper of the game. I don't mean ranged but I mean that ass hole that everyone hates. You're running down an alley and all of a sudden you're heads flying off and you're staring at a spawn screen before you even realize it. But unless the guy is a serious pro most snipers are complete crap if you get them in one on one short ranged combat. Similarly the sub rogue should have the power to just ruin someones day. They should be able to assassinate someone rather than the current form of mildly annoying them. In a group fight where everyone is focused on a giant brawl the rogue should be the one who sneaks in and counters the healer/support but just taking them out. If there was a fast paced FPS style combat and think that'd bring back so much of the flavor of the rogue that has been passively lost over time.