I wrote a quick 'n dirty rotation simulator for some theorycrafting relating to DW/Rend (thread), and figured I might as well post the numbers for the "ideal" (such as it exists) rotation. I hope they're of some use
These numbers are the average time between each ability use - sort of like the real-world CD of the ability. They've been calculated over a simulated 230400 GCDs (that's 4x 24-hour days) at three different hit/expertise levels. I believe the rotation I used (described below) is what most of you are using. If it's not, let me know and I'll run the numbers again.
Notes: This doesn't account for Conc. Blow's lower GCD (very slight impact overall, and the data is noisy enough that it shouldn't be a problem). It also assumes infinite rage, and zero lag.
The rotation used was a Survivability > Threat priority system. I've ranked the abilities here with the highest priority ability at the top, and the lowest priority ability at the bottom.
I put SS above Shockwave/Conc Blow because of S&B procs (which are fully simulated, in case you were wondering). The simulator keeps TC/Demo shout up constantly (but also most efficiently), assuming the abilities don't miss.
-5% to hit, -15% Parry/Dodge
Demo Shout: 28.5s
Shield Slam: 5.44s
Conc Blow: 30.55s
-3% to hit, -7% Parry/Dodge
Demo Shout: 29.1s
Shield Slam: 5.34s
Conc Blow: 30.55s
-0% to hit, -0% Parry/Dodge
Ok, great, but how do I use it?
Demo Shout: 30.0000s
Shield Slam: 5.27s
Conc Blow: 30.53s
Honestly, if you're asking that question, you probably don't need to be using it
However, this can be of some use for determining what you need to work on in your rotation (for lack of a better word). Once you get past the initial sundering-up/debuffing phase of the pull and start into your tanking rotation proper, the highest threat output you can achieve while maintaining highest survivability will give you the above numbers. You could actually take your WWS and divide the time in seconds by the number of times you used each ability to compare how you do vs. how the ideal tank.
Of course, this is not without its limitations (the ideal tank does not need to blow CD's!), but it might be of some help