The issue is that it just doesn't fit with the given role: RDM was a melee fighter, but it was never a frontline fighter because it lacked the survivability.
I missed this the first time I read through this thread and caught it as I was rereading some stuff just now.

I'm not exactly sure where the lack of survivability comes from, considering that in older FFs it could wear virtually all but the heavy plate armors, heal itself if necessary, and in XI, had Phalanx and Stoneskin to further back it up. Nor do I quite understand what exactly you were trying to say, in case I misinterpreted it.