First of all I would like to say that the following comment only concerns PvE, because I think rogues still are very strong in PvP (maybe even too strong when fighting warlocks

).
The sole purpose of a rogue in pve imo is, and always has been to deal heavy single target dmg. No matter what changes Blizzard have made since day 1, there have always been a way for a skilled rogue to occationally top the meters in many boss fights. This is what have changed with WotLK, now the only way to top the meters is exploits:S.
Ive always played rogue, Ive raided hardcore at times and some times Ive played more casual, but Ive always felt that thrill from trying to beat other good dmgdealers on meters. Now I mostly feel the agony from having to fight like a maniac to stay above other melee classes with much greater survivability and diversity than the rogueclass, like retribution paladins and dps warriors (with the warriors beating me in many fight I'm supposed to own, like thaddius and patch). In Vanilla WoW and TBC I was consistently a top 5 dpser, in WotLK with pretty much the same ppl as TBC Im now struggleing to stay in top 10. Equally geared warlocks, hunters, SPs and mages are pretty much untouchable, and in combat spec Im often beaten by fury wars and DKs, and struggleing with retri palas, shamans and tanks

(DK and Feral if there are multiple mobs). Might be because Ive always been a crappy player only beeing able to do good dps, because I was a rogue, but since Ive always been one of the better rogues in my guilds I dont think thats the issue... I think we have been balanced into oblivion.
From my perspective Blizzards idea of balancing has now reached a level where the pure dps classes have become greatly inferior to multispec classes, because we will never be able to offer the same diversity and now we can only at best offer the same dps. I can understand why Im beeing beaten on trash where AoE dmg gets the job done as it is now and tbh I dont care about that, Im not an AoE class and I dont want to be one, eventhough its my AoE dmg abilities Blizzard consistently have buffed and seems to keep buffing in WotLK. If I wanted to be able to AoE I would have rolled a mage or a warlock...
Regarding specs I must admit that I havent tried subt yet in WotLK, since I dont want to use the HaT bug and make us look better than we are (and thereby contribute to Blizzard overrating rogue dps as it is now). But neither in Muti nor Combat (Fist/dagger) have been able to get up where I think a rogue should belong (at best Im 3-5 on patch if I get all group buffs), but more often Im 6-7ish. This really pains me since my time to shine is supposed to be when I deal heavy dmg. With the threat tanks deal these days our low threat per dmg has become useless as well, and ToT is only useful if you have another rogue in the raid whom can return the favour.
It can even be hard to get a raidspot now because it doesnt matter what class you bring dpswise, and since all other classes in some way can contribute with buffs/debuffs a medicore arms warrior or enhc. shaman can sometimes be better to bring than a good rogue, because they with their buffs increase the overall dps more then the difference between a rogue and other melee classes. Ive yet to see the day my RL tells me that Im in because they find it amazing that I can move around in stealth, pickpocket, or because I in the future might be able to take only 50% of the AoE dmg that will easily be avoided by ranged dps.
After reading what I just wrote, I can see that Ive done something I swore I'd never do... Ive made a whinepost, but hope Ive managed to address the issues that atm is making many rogues sad pandas and thereby added to the discussion by making more brilliant minds than me think about solutions.
I truely deeply feel that Blizzards approch towards balancing the dps of all dpsclasses is making a pure dps class, as rogues are, very much less desirable to play.