Mr. Robot In Depth: Tank Metrics


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What should a tank look at as a simple metric on a combat log?  Damagers have DPS, healers have HPS, tanks have… what?

Our logs will give you three easy numbers, and this post described how useful they might be.

Damage Taken

Total damage taken seems like a natural way to compare or rank a tank.  Unfortunately it doesn’t work so well for a variety of reasons:

  • Most fights require tank swapping or different jobs for each tank, which can lead to big differences in total damage taken.
  • Some tank classes just take more damage by design.

So while not a useless number… it isn’t all that helpful either.


This is a metric created by some theorycrafters, and you can read full detail about it here.

TMI was created primarily as a theoretical metric to be used in simulation and mathematical modeling to help determine the relative value of different stats on gear.  We use TMI and simc to help us create our tanking stat weights on AMR and find it to be very cool and useful.

We calculate it on combat logs… but it is of pretty limited value on logs.  In theory it should tell you how spiky your damage is — do healers see your health bouncing all over the place and go into panic mode, or is it steady and predictable?  Good concept and metric, but the numbers you see on combat logs don’t translate into actionable information usually.

At lower difficulties where the damage spikes just aren’t that dangerous (basically anything below Mythic), the metric can be skewed and give a number that is hard to interpret.  Even at Mythic difficulty, you only really want to use the number as a relative comparison of tanks on the same fight and probably of the same class.  You don’t want to use TMI as an absolute metric where value X is “good” and value Y is “bad”.

New!  Healing Required / Second

We have created a new metric with our latest log update. We just call it “healing required per second.” It’s THIS easy: when a tank is “main” tanking a boss, how much healing does he require outside of what he can do on himself?

This is NOT a one-size-fits all algorithm, trying to smush each fight into a metric. We code each boss individually so you are only looking at what’s important for tanks in each fight. Every boss is customized :)

This metric is live for NEW logs. Go to the Damage Taken report to see it. If you want to test it out with a log you’ve already uploaded, you can change the file name and upload it again. NOTE: It will show duplicate logs if you do this though.


How it’s Calculated:

  1. For each boss encounter, we define what constitutes “main” tanking.  The goal isn’t to necessarily capture every point in a fight where a tank is taking damage, but instead to define the “main” and more consistent parts.  For example, on The Butcher both tanks are considered “main tanking” for the entire fight.  On Mar’gok, a tank is only considered “main tanking” when Mar’gok is hitting them.  A tank will certainly take damage from the different adds in the intermission phases of Mar’gok, but it is highly variable depending on which adds and what kind of strategy your team uses.  So we cut it out for the purposes of this metric.
  2. For the time where a tank is “main” tanking, we total up how much damage they took, and subtract self-healing and self-absorbs.
  3. What you are left with is how much healing your healers would have to do to keep the tank alive during the more consistent tank damage phases of each fight.

This metric does not tell the whole story of course, just as HPS does not tell the whole story for healers.  But we think that it is far more useful than total damage taken and for more practical than TMI when looking at a log.

Here are a few potential uses for this metric (assuming it works out over the next couple weeks, we’ll be keeping an eye on the log data):

  • Rankings.  We think this number is a decent candidate for tank rankings and percentiles.
  • Actionable Benchmark.  A damager can look at DPS on a fight and try to improve it the next time he does the fight.  We think this number can function similarly for a tank: try to reduce it each time she does the fight.  In general a tank who uses active mitigation and times cooldowns will take a lot less damage during these main tank phases.
  • Adjust Tank Assignments.  If you notice that one of your tanks is requiring a lot more healing than another on a fight, but they are of equal gear and skill… it is a good indicator that maybe your strategy for the fight is off.  Maybe a more even tank swap would result in a better damage split?  Depends on the fight.

Want to see a log of it in action? Any log uploaded in the past 2 weeks shows it. And here’s an example from our raid’s mar’gok’s attempts last night:,d=2