I can confirm with 100% certainty that rogues are bugged with the crit tables.
How do I know this?
I had an ambush leveling spec which, with remorseless attacks and Improved Ambush (and my base crit rating), gave me a 100% chance to critically strike. And I did critically strike…nearly 100% of the time. There were a handful of times that I did not, despite my critical strike chance for ambush being 100%. Clear bug.
I am also combat daggers, with a 55% chance to critically strike with my backstab ability (without any buffs). I crit on average around 30% of the time, over a very large sample pool. There is definitely something wrong with the crit tables from specced talents.
On a side note, I found an odd bug. If I have 5 points into camouflage, my stealth cooldown is significantly reduced. However, if I enter into a dungeon while stealthed, and then unstealth my character inside the dungeon, my cooldown is not reduced - it is the same length as if I did not spec into it. A very minor (and not really game-affecting) bug; but it does show that there is something wonky with the talents and instances for rogues.