You are one of the most narrow minded posters I've ever seen on any forum. How does a job that doesn't have Astral Fire II/III, can't use Flare or Enochian Fire IV going to Faceroll over BLM?
Yes, the point is to make jobs feel/play different that don't overlap each other but still function similarly. They are not supposed to be 100% alike. Overpower is also conal, you complain things are too similar and will faceroll over existing jobs and at the same time complain they are not similar enough.
That's why a RDM Tank would have Phalanx that increase defense and increases enmity (just like Shield Oath, Defiance, Grit), Aquaveil that decreases spell interruption/allows for parry while casting, Fast Cast traits that reduce but doesn't eliminate casting time. Blaze Spikes that increase Enmity for all fire based spells.
Because RDM is iconic to FF and molding Sword, White Magic, Black Magic into a usable job without trashing balance can also be creative.
Why does that matter? PLD is not casting focused, RDM would be. And WAR has Inner Beast, Storm's Path, Thrill of Battle, Equilibrium, Blood Bath all of which give them HP back in one way or another. RDM would be a lot less tanky than PLD so it would want to have more self curative spells, abilities and traits.
The point isn't to make RDM exactly like PLD or WAR, it's supposed to be different enough from the other tanks so that people want to play it but still similar enough so that you can swap them out in DF and not notice a difference. and you would be able to raid with a DRK + RDM tank combo as well as you can with a PLD + WAR combo.
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No, it certainly doesn't have to be the case. But one uniqueness of RDM can be because it's the only job that does. I'm not assumng they will have those spells I want it to.
But why should they when it's very viable to make it work. People do want a tank that can challenge the utility of WAR in OT situations and RDM on paper has every capability to do that. The Black Magic to do good DPS in a tank role but not so great as to rival BLM which is the actual DPS job. The White Magic to sustain itself in similar fashion that WARs currently can but not so overpowering that you can main heal like WHM. The only issue then is utility and mitigation. It's certainly viable between Phalanx, Stoneskin, Parrying and some other White Magic it can be competent at mitigation, but nobody is going to say it's a Master of Mitigation, PLD and DRK will still edge it out. It just has to be tanky enough to not die to tank busters and it will be usuable in the current game design.