Yes, this is a copy paste, no none of this is my work, see the link for the original posting.
http://daforums.bioware.com/forums/viewtopic.html?topic=706563&forum=135&sp=45
Somethings to remember...
-Armor piercing is only improved by (CUN-10)/7
-Expose weakness is only damage (CUN-10)/3
-Only (base damage + modifier damage) is multiplied by crit modifier, NOT AP or Expose weakness or any other 'bonus damage'
-Combining the above three together, and this would mean that the damage outside of lethality CUN damage bonus would be minimal at best
Basic formula for backstab damage is this..
base dam * crit modifier - max (0, armor - ap) + expose weakness damage
And considering full sized weapons has higher base dam from having better attribute bonuses, it stands to reason that from a damage per backstab hit, full sized weapons have the advantage as this higher base dam would completely overshadow whatever damage the CUN rogue gets from higher AP and/or expose weakness.
But what about attack speed? This is an example way back then, but it should still stand since DEX isn't yet implemented on daggers (but the .85 modifier still is)
Longsword (7.7 base damage per hit, listed damage is in character screen with an offhand dagger, whose damage is not listed)
20 STR - 15.4 damage
23 STR - 16.5
Difference - 1.1
Dagger (4.4 base dam per hit)
20 STR - 10.7
23 STR - 11.6
Difference - 0.9
Mace (5.5 base dam per hit)
20 STR - 11.4
23 STR - 12.5
Difference - 1.1
Note this is the LISTED damage in the character screen, meaning this is already divided by some amount of time already. Meaning this is already equalized in terms of weapon speed, as this is damage over a certain amount of time arleady. And as you can see, longsword and even mace already has the advantage.
Even ignoring the base damage, just looking at the difference for each point of attribute would mean that full sized weapons would pull out even more. And we're not talking about Waraxes either, which scale even better per attribute point put to it.
Also note that this is with daggers receiving 100% STR bonus... when they patch it to be 50/50 STR/DEX, you're going to get EVEN LESS per point.
Which of course favours high STR/min DEX/min CUN rogues over min STR/decent DEX/decent CUN rogues no matter how you slice it. Full sized weapons, even in dual wield, have higher listed DPS and this DPS also scales better per point of attribute, so in no way dagger outdamages full size now or in the future.
An interesting thing to note is these are the same STR with the same weapons, but with NO offhand weapon
Longsword
20 STR - 18.8
23 STR - 20.8
Difference - 2.0
Dagger
20 STR - 17.1
23 STR - 19.2
Difference - 2.1
Mace
20 STR - 13.9
23 STR - 15.8
Difference - 1.9
So what happened here? Daggers whoscaledslower in dual wield now has the highest scaling?
So from this, we can conclude that dual wielding imposes an attack speed penalty for both hands, since I have NOT noticed any significant change in damage PER HIT. But considering this REALLY impacts daggers in the character creation screen, we can safely assume that this penalty to attack speed by dual wielding is an additive one, as it greatly reduced their listed DPS once you make them dual wield.
For example (numbers made up, but they illustrate the point), if dual wielding increases the time interval between attacks it by 0.5 seconds, a dagger with a base of 1.0 seconds per attack will now become 1.5, reducing DPS by 33%. A Longsword on the otherhand, if it has a time interval of 1.5 seconds, and dual wielding makes it 2.0, then it only has reduced DPS by 25%. Which, while not the exact reduction, is inline with how badly dual wielding daggers impacted the listed DPS in the character screen.
And for the record, the missing manual says momentum bonus is multiplicative (Georg mentions that its a straight 30% increase in DPS), so it should affect your DPS the same scale no matter what weapon you use or what wield ****you use.
In conclusion...
If you want max DPS, stick with the STR focused rogue. And for the love of the Maker, skip daggers because of how badly it gets nerfed if you dual wield it. We're not talking about how the STR rogue gets better attack rating as well, or the fact that the higher base damage of the weapon benefits backstabs much more than the high AP value the dagger has.
Besides, there are two waraxes that greatly benefit the rogue, and both have much better attribute bonuses. Granted one does not require attributes at all, so both types of rogue can use it, but the STR one benefits more because they'll have higher STR than the CUN rogue has CUN.
Of course, if you want lockpicking as well, Cunning is the way to go, as there are chests that needs both lvl 4 deft hands AND very high cunning in order to be picked. But for the purposes of DPS, its very clear that its inferior to a STR rogue wielding full sized weapons.
tl;dr
Depends on your party make-up. If you have ANOTHER rogue who can lockpick for you, then go ahead with a STR focused build. If not, its better you go for DEX/CUN despite of inferior DPS, because 22 CUN + lvl4 deft hands is not enough to pick all the chests you come across.