Rynas, I'm getting numbers that are a bit off, but for other reasons. I plugged in all of my stats: 117 weapon power, 55% atk, etc. And from the front on a def 0 enemy (undead archers) I should be doing about 181, but I'm actually doing no less than 200 per hit, sometimes up to 225! Flanking hits are likewise a bit boosted. Either a perk I have somehow isn't getting through, or there's something up with the calculator posted. I'm not sure!
Happily, however, it looks like spinning blades at least DOES do additional flanking damage. The damage scales appropriately, although the ring seems bugged as it says it deals 100% of weapon damage but its numbers range a little bit lower than most basic attacks do, although that's probably luck. I am guessing that twin blades -also- does additional flank damage, as the numbers I'm getting from flanking attacks with it are monumentally higher than what's predicted on the spreadsheet, but factoring in an extra 57% flanking bonus on top of it makes it all work out. I also crit a lot more from the rear with these abilities, which means that rear-crit perk works for abilities as well!
Of course, since that's how everything works out, it's tricky to find the best balance to get the most damage and utility out of rogue! I can pump flanking damage since I'm likely to be behind enemies almost all the time, or I can focus more on critical chance because my crit damage is about 101 from my super high dex, and I regen stamina with every crit. On a multi-hitting move like spinning blades, with a high enough crit percentage bonus I will probably regain stamina, letting me use my abilities that much more often. I'm under the impression that runes can't crit OR deal flanking damage, although if they can then I definitely want to be cycling in the appropriate slaying rune for whatever enemy I fight.
So the real question is: factoring in the loss of damage from flanking with the bonus damage from crits (Which you so graciously have a window for comparing), how much loss is 'worth it' to get the stamina regeneration?
On a side-note: how does Vitaar work? Is the damage bonus a % attack boost? Is that number added directly to your weapon damage? If it's a straight add to weapon damage then Qunari would be most ideal as rogues or mages due to the low damage-per-hit of staves and daggers.
Edit: Whoopsie! I didn't see your post while I was doing my experiments! The damage -does- seem off from what I'm seeing, I very rarely get damage as low as I'm seeing averaged on the calculator. You have to add in flanking damage automatically, but you can usually just figure out what will apply to the end anyway - for example if I'm using a ring on spinning blades they SHOULD do 100% of regular weapon damage (They don't), so you can just use the regular basic attacks to figure out how much damage per hit, and then just multiply.