Meteor is non-elemental. That old talk about monsters' Meteor being dark damage is just falacy from level 75 era.
Besides DT- sets, RUN has incredibly high MEva and MDB, especially with lots of JPs. At this point, Valiance and Vallation are mostly to protect your party and for Inspiration.
There's still a misconception about RUN as tank. It's not "how a RUN can survive magic damage like an Aegis PLD"? It's the other way around: "how a PLD can dabble in RUN's levels of magic defense"? "Using an Aegis", of course.