Sonic barrier is max of around 110 hps in hybrid (1000/9s). You're forgetting also that 10% of your internal resistance comes from the Inquis/Consular buff which everyone would have in nearly any pve content. I would also include mitigation stats in the calculation of survivability rather than simply taking your hps divided by damage taken. Either way the point isn't that your hps are insignificant mitigation, it's that the differences between the hps across the tanks classes are relatively insignificant, especially for hybrid juggs vs assassins.
The value of Sonic/Blade Barrier is computed as the following function:
((7085 * 0.05) + (power * 0.17 + force-power * 0.17 + strength * 1.11 * 0.14) * 1.05) * 1.2
For a pure defense/immortal guardian/juggernaut in augmented Campaign gear, that gives me a value of 1142.76. That's 95.2304 HPS. If I drop the cooldown to 9 seconds, the HPS goes up to 126.9738.
That's a pretty wide gap from the 160 HPS that a shadow/assassin can reach, and the 0 HPS that a vanguard/powertech will achieve.
Oh, and I'm not forgetting that 10% of resistance is from the Consular/Inquisitor buff. Something is apparently weird with how Ask Mr Robot computes resistance, since it claimed
to be including all the buffs when apparently it wasn't. I suspect the actual resistance for a vanguard/powertech is 19%, but I need to verify.
The percent of mitigation (and therefore survivability) of hps varies depending on how much damage you are taking as well whereas mitigation stats are relatively constant percentages except when force/tech attacks increase dramatically which is typically rare. So your hps might be slightly better on the Dread Council with the DoTs but that 91 points of defense would be better on Operator or Terror as you are taking nearly twice as much damage and hps don't scale with damage unlike pure mitigation.
Yes, I consider the mean survivability contribution from HPS. On current content, all bosses hit for nearly the same amount (to within 10%), so the mean is actually going to be fairly accurate. I have extremely precise data on pre-mitigation DPS for all bosses in the game on their hardest modes, so I am able to make such calculations.
Also I can absolutely count mini CDs as active mitigation if they're the sort of thing that is used consistently more than once per fight. Only true emergency CDs should not be counted.
If they're being used in a steady-state, predictable rotation, then yes (e.g. Dark/Kinetic Ward). If they're not being used in rotation, then no, you cannot count them. If it's not in rotation, then it is a situational ability used in response to something else that happened in the fight. You can't consider situationals in a smoothed statistical model.
All of this is not to say that this spreadsheet is a perfect comparison of tanks but it's a damn fine tool to use as long as you keep in mind these class mechanics. To pretend that it's useless for comparing is truly naive.
It's fine for comparing tanks if you want a severely incomplete picture of relative tank survivability.
The reason I get so up-in-arms over things like this is it is precisely this sort of spreadsheet that led to the (still widely-held) belief that vanguards/powertechs are the only tanks worth having, and shadows/assassins are severely under-powered. People have a tendency to underestimate the value of a tank's self-heal (case in point: your earlier post). Spreadsheets like this encourage such underestimation since they fail to take the self-heal into account at all
Comparing tanks by using this spreadsheet is simply ignoring major components of steady-state tank survivability. It would be like comparing the DPS of a Maurader to that of an Arsenal Mercenary without counting the damage from Unload. It's silly, and it doesn't really give you an informed answer.
This spreadsheet is very
good for weighing defensive stats and optimizing them against each-other. No question about that. It's just an extremely poor tool for performing tank balance comparisons.