Are Magical damage taken- and Breath damage taken- mutually exclusive separate things? That is, MDT- wouldn't reduce damage from Dragon Breath, and BDT- wouldn't reduce damage from Hurricane Wing. In other words, my question is would MDT-3% work on Dragon Breath and Hurricane Wing? Thus making equipping a BDT-3% equip in the same slot pointless. (This is a purely fictional example.)
The only thing I can find on alla or ffxiclopedia about this subject is that Hydra Mail has Physical Damage taken-3% and Magical Damage taken-3%.
It seems it would just have Damage taken-3% if there wasn't a 3rd separate category, BDT-%, that is not included in MDT-% already. Who knows, maybe it's just a dev who didn't make the connection.
I'm curious about this for a specific use in Ballista, (not for Fafnir or any other wyrms) and I figure no one would know better than Paladins.