I agree with it considering how easy is to get a good output with not such high effort, maybe except for WAR, honestly I dont' think that it is very simple to use it, an inexperienced player will just run into the enemy party and badly die in 5 sec, or live a lot keeping defiance up ut achieving just some random kill.
Taking in consideration the squishiness of different classes, I think BLM and PLD has the highest one and really make a big difference for a class survivability (not talking about healers).
Probably we should put a list of the top tier job for different situation, like "Top Killer", "Survivability", "Party support", "Friendly to use"...
