Breaking things down into "avoidance" and "mitigation" is a fundamental (though very healer-centric) way of describing the two ways in which tanks manage to take less damage than another class/job would in that same role.
Except there are more ways to tank than simply avoiding or mitigating damage.
City of Heroes has regen tanking, someone who is neither good at avoiding or mitigating damage. He just regens health like crazy and relies on defenders (CoH equivalent of healers) to make him tougher rather than to directly heal him. This is fundamentally different than the established 2 categories.
There's also the way bosses tank. It's very unlikely you'll ever see a game implement it for characters, but bosses tank through massive hp. They neither avoid damage nor mitigate it (to an extreme extent). They just have enough health that they can eat it.
In fact, the two categories themselves are more similar than most of the methods within them. 25% dodge chance is more similar to 25% armor mitigation than 25% hp regen is to either of the two.
If you were to graph the healing needed over time for every tank, those graphs would end up taking one of two general shapes. On the one graph (the avoidance tank) you'd have periods of no healing needed interspersed with periods of needing a lot of heals. For the mitigation tank, you'd have a consistent amount of healing needed, with very few spikes or periods where no healing was needed.
Actually, assuming spike damage could never one shot the dodge tank, ,f you take the limit of the two tanks as time approaches infinity then they are exactly identical. The sole two categories people are trying to establish are flawed.
From a healer's perspective, regen tanking IS mitigation.
No, it most certainly isn't. Regen tanking doesn't scale with damage. The more DPS a mob produces the more damage a armor mitigation tank or a dodge tank is able to avoid. A regen tank doesn't scale at all with mob DPS. It's fundamentally different than the other two.
If people understood math better then they would see the problem with trying to break all tanking into either damage mitigation or damage avoidance. Certain elements they've group under those categories work drastically different than other elements. Some of the differences are far greater than those of dodging and flat mitigation.
The rule of taxonomy is that elements within each category should be as similar as possible while elements across each category should be as different as possible. This silly two tank system people are trying to establish blatantly spits on that rule.
There are at least 4 different types of tanking. I could probably set up more categories if I thought about it for longer, but I want to make a point that 2 is simply not enough.
A boss produces a certain amount of DPS. If elements of this DPS formula are change then tanks that are similar will change in the same way and tanks that are different will change differently.
Let's start with armor mitigation (25%) and dodge tanking (25%). As the interval for each hit of the bosses DPS approaches zero these two tanks function identically. That is, if the boss does a million tiny hits per second the dodge tank works nearly identically to the armor tank. However, as that interval increases that changes. The dodge tank becomes more variable. At a certain point there is an amount of damage where a dodge tank can be one shot but an armor tank cannot. This shows that the tanks are fundamentally different.
Now let's compare armor tanking (25% mitgation) to regen tanking (regen health per second equal 25% of the bosses current DPS). At a constant DPS regen tanking works similarly to dodge tanking. And there is a point where a regen tank would be one shot, the same point where a dodge tank would be one shot, that an armor tank would not. However, if we increase the bosses' DPS both the armor and dodge tank increase there effective mitigated damage. The regen tank does not. He regens a constant amount of health per second. In fact if the boss is weak enough with low enough DPS then the regen tank will never die, whereas an armor tank and dodge tank would eventually die without support. This means the regen tank is fundamentally separate from the other two.
Now let's examine a blocking tank. A blocking tank blocks a certain amount of damage every hit. Similar to the regen tank he doesn't scale very well, but he scales pooorly differently than teh regen tank. The blocking tank can theoretically tank infinite DPS, so long as each hit is for a damage amount below what he blocks. If he blocks 50 and the mob hits him for 50 then it doesn't amtter how fast the mob attack, whether it is once per second or a million times per second. He will never die. However he can tank low dps very poorly, so long as they are heavy, slow hits. He is fundamentally different from the 3 others.
Just playing around with total DPS and the ratio of damage to attack speed you can see how each of these tanks is complete distinct from the others.
I didn't even cover blink tanking, which is basically the inverse of block tanking and is complete separate from dodge tanking. a Blink tank can never be one shot or killed so long as the hits are slow enough. Edited, Jun 28th 2009 2:48pm by Allegory