Back in the day, I would have said hunters, bar none, since they are pure DPSers with great survivability via pets and a sweet travel power (Aspect of the Cheetah). They're also incredible at kiting, which is really noteworthy since kiting is a great way to solo nasty elites that give other classes trouble (many elites are outright immune to stuns, sadly, and most CC heals them to full). That said, the competition is a lot stiffer now. After all, the Feral and Enhancement trees for shaman and druids are a lot stronger than they were back at release, and both of those classes have travel forms that can best Aspect of the Cheetah. Plus, it's not even really that huge of a deal now to have sweet travel forms because everyone can get a mount at 20 anyway. The game's in a really healthy place right now in terms of leveling parity. If you must be the first guy to hit 80 on your server, I'd say go hunter, but other than that I wouldn't worry about it.
As for rogues, I'd say that we're actually pretty vanilla from a farming at 80 and leveling perspective. Basically, there's two big reasons why our damage is so potent in a group setting. Unfortunately, neither of those mean much when we're going about our business out in the wild.
1. We scale really,
really well with epic gear and raid buffs. We're one of the top DPS classes in the game right now because we scale so well. We don't even have any real melee "junk" stats. Armor Penetration? So good that I'll soon be gemming it. Haste? Buffs our energy generation and our massive white damage. Agility? Yes, please! Heck, we do so much poison damage now that I can even get a noticeable DPS increase from a moonkin's spell crit aura! The downside to this? I'll just go ahead and quote Blizzard directly:
"one of the disadvantages of scaling so well in a raid scenario is that you need to start at a lower baseline." The higher you go, the farther you have to fall. We still do competitive DPS solo, but without full buffs we actually do regress to the mean. I curb stomp hybrids and most casters in raids, but solo or in a 5 man? I'm just another dps class.
2. Finishers kick ass. Our best sustained DPS moves are Slice and Dice and 5 point Ruptures. Hell, Slice and Dice is so good that we're not even really raid viable without it. Key word is "raid viable," however, since the move is actually pretty vanilla against non-elites points since it only helps sustained damage and because the buff is so short that it's often counterproductive to chain together multiple mobs just to get full use out of it. Rupture is even worse. Most non-elites won't live long enough for us to run up 5 combo points on them, much less take several ticks of the dot. After all, warlocks only get such good use out of dots because they can quickly chain cast them against multiple targets and then finish them off with a few blasts of direct damage. Rogues have the formula backwards.
So, really, rogues are perfectly competent soloers. Our dps is as high as anyone's and stealth is pretty alright. But our dps isn't actually outright
better in solo situations and our utility is kinda low. Stealth is cool, but frankly, I don't use it all that much simply because stealth is slower than walking or riding. Overall, we're good but nothing to write home about.