First of all, many of our talent choices bring minimal to no value in terms of our DPS. To illustrate this, I'm going to look at each tier of talents and point out their shortcomings (and this is probably obvious to most rogues already).
<15> Nightstalker is the talent I chose in this tier because it at least provides an opening attack damage boost by 25%. However, compared to the talent it replaced (which granted a damage boost for 30 seconds after exiting stealth) it pales in comparison. Subterfuge and Shadow Focus are quizzical talents.
<30> Deadly Throw provides the best situational DPS in this tier, whereas Nerve Strike and Combat Readiness only add to the recent plethora of rogue survivability.
<45> MORE survivability! Absolutely none of these talents bring any damage to the table.
<60> Even MORE survivability, except this time the focus is on mobility. Shadowstep may prove to be better than the other two talents depending on the situation, though I chose Preparation since it gives more flexibility on CD resets. And remember when preparation used to reset the CD's of other damage abilities like Adrenaline Rush? That would have been much more useful here.
<75> Prey on the Weak is the clear choice for DPS, but the downside is that you're forced to use abilities that lower your DPS (in terms of a raid environment, and in that case most bosses are immune to the abilities required for use). Paralytic Poison and Dirty Tricks are obviously geared more for PvP, so while they don't directly increase DPS, they provide more opportunities to do DPS.
<90> FINALLY! Some REAL damage talents! Shuriken Toss is a great idea for rogues that provides actual ranged DPS. However, it's another situational ability, and it's obvious that if you're able to melee, then this ability isn't as useful. Versatility is a talent that really shouldn't be a talent. Redirect just shouldn't have a CD to begin with. But again, this is yet another situational talent where it is really useful if you're fighting multiple mobs and have to switch back and forth for whatever reason. But for single target, this talent is useless. I chose Anticipation for this tier, and it was because of previous raiding experiences. I remember there would be times where I would have 4/5 combo points and use and ability that had a chance of providing an additional combo point. Well, this talent was the answer to that missing combo point. It would no longer go unused. It actually works pretty well when using AR and Shadow Blades, as the combo points build up pretty quickly and usually overflow.
Things would be looking better for us if we had more pure DPS talents, instead of a barrage of situational and survivability talents. I don't seem to remember survivability being a problem in the past, so I'm not sure why Blizzard insists that we have an arsenal of it all of the sudden.
Another key issue that I've found with our DPS is energy regeneration. Now, I leveled from 85-90 as Assassination, and I found that from my opening attack until the target was at about half health, everything was fine. But once I hit the 50% mark and had to wait for my energy to pool again, it seemed to take a lot more time to finish killing the target. I noticed the same thing at 90 when I specced combat for dungeons. This time, the energy regeneration was much more noticeable from the start of combat. And while combat provides better damage when facing multiple mobs, it still takes what seems forever to kill them because of the super slow energy regeneration. Keep in mind, I'm talking straight up combat without cool downs, it's obviously much faster with CDs. I can't comment on Subtlety's playability since I haven't specced it in years, but I hear it's not much better.
So what's with the slow energy regeneration? Is it possible that since haste effects it, somehow the equation was skewed by haste rating changes going from 85-90? Possibly. But if that were the case, the easy fix would just be to double the effect that haste has on energy regeneration.