Right now, RUN can happily tank level 99 content (Arch-ultima/omega etc). That's not bad considering we have no merits/AF/relic/empy gear, nor do we have a 'special weapon/grip/ammo' since we can't use shields.

Once we get merits/af/empy/relic gear, RUN should be able to tank adoulin content (if SE don't change their minds and give merits etc for DDing instead of tanking). But we shall see.

Tanking on RUN requires more thought than tanking on PLD, sure, but that doesn't mean that the job is bad.