As it stands Parrytanking has been tried before and failed. Unless you want to give RUN the same type of JA that NIN has that allows for a massive spike in Parry rate which goes against your idea of making the job "unique" I don't see what you think parry is going to do when your rate is floored on most things significant.

As for evasion, isn't that the realm of NIN and DNC already? The reality is with as many jobs as FFXI has something's got to give and this case its probably best to give players access to native cures on the wannabe tank job. It's a matter of self-sufficiency and the ability to choose more subjobs from the current options in addition to supplementing your decent eva and high parry rates.

NIN has evasion and shadows.
PLD has defensive JAs and healing magic.
RUN has evasion and parry and some light regens.

RUN has access to similar gear, wants to be the go-to on magically oriented mobs and that's unique but its a DD without any real ability to support itself and so its MP pool goes to waste.

Giving the job cures still differentiates it from PLD and NIN by having a little of both while not having everything the other two tank classes possess. It would have greater survivability but pale in comparison to PLD, evasion but not the physical damage mitigation abilities of NIN and still have a niche as a damage-oriented support tank that specializes in magical damage.