Evasion tanks wont really work with how most end game mechanics work... Lets look at tank swapping, some of the most hard hitting attacks are ones that require tank swapping (eg. Titan, Ultima, Ifrit, T6)... if a tank could evade those attacks it would be pointless to ever bring a PLD or WAR into those fights. If SE made those attacks always hit then an evasion tank would have to have just as much life as a WAR and if it didn't have the life it would need just as much mitigation skills as a PLD. The other bad part about an evasion tank is RNG, if the RNG is crap (sometimes the case with WARs) then you could end up not evading a couple hits in a row and boom dead. To counter this again the evasion tank would need a large health pool to decrease the chance of RNG killing them just like WAR, or have mitigation skills just like PLD. I am really interested to see what the next tank will be, its just with the current direction of battle mechanics I don't see how an evasion tank could work.

Also, that video has exactly the issue I am talking about... oops the RNG gods didnt let you evade that attack, boom one hit KO.