Stacking stats.

There are several particular stats you want to look for as a rogue. In general: agility, attack power, and critical strike; will usually do for most rogues. Some of the other stats that aren't quite as sought after would be hit, expertise, haste, and armor penetration. Hit and expertise will eventually "cap" when stacking these stats as there is no such thing as hitting your target more than 100% of the time or being dodged less than never. Armor pen will also cap out at 100% but would probably require some extreme lengths of gear mutilation and losing hit and tise caps to achieve. Haste increases attack speed and has no cap (or at least not one that is achievable in game) and is a generally overlooked stat. Since hit and expertise are just stats you are forced to cap lets discuss haste against armor pen. Armor pen reduces a targets armor against your attacks, therefore increasing your physical damage dealt to that target. Haste merely makes you attack faster, neither are bad stats but depending on your spec one may be worth more than the other. A combat rogue focuses on high passive energy generation along with an extremely powerful main hand instant cast attack called sinister strike. An assasination rogue uses attack skills less frequently and focuses more on poison damage. Since the damage dealt by poisons is nature damage instead of physical armor pen is worth a bit less to an ass rogue than a combat rogue. Haste however will increase the ass rogue's attack speed and therefore his poison application rate. Faster attacks will also generate more energy for an ass rogue due to his focused attacks talent which causes his melee critical hits to generate energy, as opposed to combat rogues whose energy comes primarily from passive bonuses in their spec. In short, armor pen for combat, haste for assasination, and if you've specced sub for raid damage I'd encourage you to download recount and rethink your spec.