I completely agree with Loom. Heck, even if they kept the target function, would still be as good as NIN's.

But I think you forgot 3 spells on that list, they being Dragon Force, Diamondback and Chelonian Gate.

Those are the tankbuster mitigators, yet they have a glaring flaw, that is a 2.3s cast time. Unless you're perfect on time with when the boss will cast the big hit, for some of their abilities, is really stressful to press them on time, beause that cast time is nearly the cast time of some tankbusters themselves. Also, they are not oGCDs... this means, that if you got your GCD rolling, you'll hae even further delay in pressing the button.

They are really unreliable because they are being applied to situations that the tankbusters were designed with the fact that the mitigators of the other tanks are abilities with no cast time and off global cooldown. I'm not sure if this was an intentional design, but sadly is what keeps me of trying to tank hard blue mage content. I've made it before, but the stress of dealing with unreliable tools is not worth.