Quote Originally Posted by Alwryn View Post
With the current design philosophy of ARR, a evasion based tank would break the game. Let's use the ever present twintania and extreme modes for examples. Firstly, we need to come to a understanding about evasion tank survivability. That is, for any semblance of balance, it's primary mitigation comes through evasion; meaning that it can't really take a hard hit. A obvious, but needed statement.
You're remarkably uninformed about tank design. There are 2 aspects of a tank that have to be balanced: eHP (the amount of premitigation damage that a tank can take in a single blow discounting any and all RNG effects) and mean mitigation (the effective increase in healing received based upon your mitigation effects as derived from reduction in damage taken over time). Certain mitigation mechanisms will bolster one while ignoring the other (+hp increases eHP but does nothing for mean mitigation; evasion and +healing increase mean mitigation while doing nothing for eHP) while others bolster both (damage reduction reduces damage over time and, because it's always there, increases eHP as well).

If you're not completely ignorant of the dichotomy of tank mechanisms, it's actually easy to design an evasion tank. Hell, I actually outlined exactly what you'd need to do in my previous post: you give it +hp (to provide equivalent eHP) to make up for the fact that the evasion does nothing for it. You get the similar eHP as the other tanks (slightly higher to make up for the spikier damage profile) as well as similar mean mitigation, which means that it's balanced against the other tanks, no problem whatsoever.

If you want to talk about truly borked tank designs that require all kinds of complex math and design to balance them out, try looking into blink tanking, like NIN in FFXI; blink effects create *all* kinds of problems because they're controlled 100% mitigation mechanisms (which means that they're either monumentally abusable if they can apply to anything and incredibly weak if big attacks go right through them) that are charge based (which means that their performance is *highly* dependent upon the number of incoming attacks per second, which causes wild vacillations in performance based upon the number of attackers and their attack speed).

The only time tanks get borked is when the designer is ignorant of the actual mechanics and balance constructs involved (like conflating eHP with mean mitigation or assuming that there is only a single metric with which to measure tank survivability). If you actually know what you're doing, it's pretty simple as long as you understand the mechanics you're electing to deal with.