Rogues should be choosing gems that support their main attibutes.
Agi, crit, hit, ap, stam.
Not necesarily in that order. Different specs have different priorities.
Does this mean you should choose a +16 ap gem over a +4hit/+4agi gem if you are a sub mut speccd? Not necessarily, as you still want to maintain some balance between those attributes. Some #s to keep in mind(and these are what I use for my guild to determine who's ready for raids).
Requirements for raiding for all rogues:
HitPoints --- 6.5k+
Gear --- 1-2 greens at most, no green weapons, prefer at least 1 epic wpn(Aldor, Scryer, Consortium, Keepers of Time)
Other Requirements/Stats I will be looking for based on spec:
Combat rogues(sword 20/41/0) *****
Hit Rating --- 175+
This is of prime importance as you will have SnD up nearly 100% of the time, (at 308 you never miss a boss).
AP --- 1350+
Crit --- 20%+
Prime Attributes - AP>Hit Rating>Agi>Stam>Crit Rating
Combat rogues(dagger/fist 15/41/5) *****
Hit Rating --- 175+
This is of prime importance as you will have SnD up nearly 100% of the time, (at 308 you never miss a boss).
AP --- 1350+
Crit --- 22.5%+(technically should be higher, with a +10% built in from talents)
Prime Attributes - AP>Hit Rating>Agi>Stam>Crit Rating
Mut/Sub rogues(41/0/20) *****
Hit Rating --- 115+
This is not as important for you as your prime finisher should be envenom when possible.
AP --- 1400+(along with crit this is your most important stat)
Crit --- 22.5%+(This should really be your primary stat as you get cps from Seal Fate with more crits, more cps=more dam faster)
Prime Attributes - AP>Crit Raitng>Agi>Stam>Hit Rating
Combat Mut rogues(41/20/0) *****
Hit Rating --- 175+
This is of prime importance as you will have SnD up nearly 100% of the time, (at 308 you never miss a boss).
AP --- 1350+
Crit --- 22.5%+
Prime Attributes - AP>Hit Rating>Crit Rating>Agi>Stam
Sub rogues(dagger 20/0/41) *****
Hit Rating --- 100+
This is not as important for you as you will be using rupture and evis as primary finishers.
Imp BackStab is required for any Sub dagger specs wanting to raid.
Enveloping Shadows also required of any sub spec wanting to raid.
AP --- 1550+
Crit --- 25%+
Prime Attributes - Agi>AP>Crit Rating>Stam>Hit Rating
Sub rogues(Hemo 20/0/41) *****
Hit Rating --- 175+
This is important as you will have SnD up as much as possible, alternating between SnD and Rupture when possible.
Requires wpn speed of 2.6 or slower in mh if you want to raid as Hemo specd.
Enveloping Shadows also required of any sub spec wanting to raid.
AP --- 1550+
Crit --- 25%+
Prime Attributes - Agi>AP>Hit Rating>Stam>Crit Rating