Rogues can be quite hard to level up. Lack of a self heal and not being particularly tough have their drawbacks. But I think on the bliz pvp forums of course the majority of threads will be about people qq-ing about other classes. A player of average skill level might fight a bad rogue, kill him easily, and think no more of it. But being stunlocked for 10 or more seconds is very frustrating, as is wearing all greens and being killed in 2 hits by a guy you didn't even know was there. They are unlikely to post on the forums about their own kills except for the memorable ones, but being killed in a way they believe they can do nothing about...well of course they're going to write about it.
I'm certainly no expert at pvp, but when I was suffering through it to get my s1 blades one thing I knew how to do reasonably well was a basic stunlock. This is an overt was of holding someone down, but other classes have similar things. Personally, getting intercepted + hamstringed by a warrior you can only hit for a tiny amount of damage is just as lethal in the end. However, you can at least "think" you can do something about it, like move very slowly around or make tiny dents in his armour.
Stealth is another example. In a BG, a rogue could pounce on you at any moment. Can be quite unnerving unless it happens a lot. But rogues need stealth. Aside from it being correct by rpg lore, it is our way of closing with the enemy. An unstealthed enemy rogue 40 yards away is a dead rogue for any ranged class, unless there is a significant gear or skill difference, or just a whole load of luck.
Indeed, rogues are powerful when they're properly geared, and the player is good. But it's the same with all classes, perhaps not all specs but arguably all classes. I don't think there's anything much in rogues that needs to be particularly buffed or nerfed. Though some sort of self out-of-combat heal and maybe a buff/debuff for raids would be nice :)