Yoshi P has already stated that there will be NO tank ability that reduces magic damage.
He doesn't even try to hide his BLM bias. (ICYMI he plays BLM)
There would definitely be some serious balancing issues among the 3 tank jobs, historically something the XIV devs have done (at best) ok and (at worst) not at all in addition to refusing to even acknowledge imbalances let alone fix them.
I like the idea of a oGCD riposte or counterstrike every time there is a successful parry. Ups the tank dps. Not sure what potency I'd use, but it has to be better than an autoattack, maybe 50 or 60?