I was curious what other players think about the idea of marking in the higher level dungeons.

My own opinion is that it helps, just not in the same way as with lower level dungeons. When I'm tanking lower level dungeons, especially before getting Rage of Halone, I mark because it is a way of communicating which mobs I'll make sure to have top enmity on. My goal here is to have top enmity on all of them, of course, but it is necessary to invest a little more enmity in one above the others for obvious reasons.

In higher level dungeons, especially with a BLM in the party, the rationale must change a bit. It is important to spread enmity around to cover AoE damage, and so you really must invest more enmity in all targets (more flash/overpower). There is a little less utility to marking for that reason.

But....